Adding a Piezo Quartz Filter

This forum is for discussions regarding System Infrastructure and Related Equipment. This includes but is not limited to repeaters, base stations, consoles, voters, Voice over IP, system design and implementation, and other related topics.

Moderator: Queue Moderator

Post Reply
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Adding a Piezo Quartz Filter

Post by krazybob »

Now that we have increased the elevation back to our coordinated altitude and location we have a repeater whose output is 15KHz from our input. Our output is 15KHz from their input. It isn't a joy for either repeater. In the past a piezo crystal has been strongly recommended. The question is not whether we should or shouldn't but where we can buy a crystal filter. Our band pass cavities can't go low enough -- 500KHz +/-.

Your help is appreciated.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

I'm assuming this is a 147.705 vs. 147.120 thing. That is a mess, no question. And you aren't going to like the answer.

Crystal filters aren't that tight, Bob. Nothing is. You need to work out the issues with the other repeater, and someone is going to have to change pairs. You can thank TASMA for the mess that is 15kHz. Your other option is to narrowband, though it's a little bit unorthodox and the user learning/equipment curve is extremely steep.

No amount of filtering, crystal filters, etc. etc. is going to fix the problem - the channel spacing is TOO tight. The problem isn't with the RF chain coming into the receiver, it's with the receiver's IF itself. Money spent on a crystal filter will be money wasted.

You need to file an interference complaint with TASMA, and somebody has to move. That's the only answer that will solve the problem. There is NO way around it.

Here's some bedtime reading for you to prove my point: http://www.repeater-builder.com/tech-in ... -20khz.pdf
tvsjr
Posts: 4118
Joined: Fri Nov 28, 2003 9:46 am

Re: Adding a Piezo Quartz Filter

Post by tvsjr »

MtronPTI (previously Piezo) is the recommended model. I've had good luck with the 4133C: http://www.mtronpti.com/resources/2133- ... 2013-07-19

That said, Chris is right. These filters are about as tight as you'll find, and they are only 20dB down at +/- 30KHz. 50KHz for 40db. At 15KHz, you'd be lucky for 10dB. And these filters aren't cheap... $600 or so, if memory serves.

You need to work with the other repeater owner and your coordination body and move. Alternatively, I suppose you could operate reverse split. I have to wonder who would coordinate an input and an output 15KHz apart...
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

I was just going to say to reverse the split and resolve the conflict. Pretty simple fix. Everybody has to agree to high side in, low side out, or something to that effect to minimize interference.
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

Bill_G wrote:I was just going to say to reverse the split and resolve the conflict. Pretty simple fix. Everybody has to agree to high side in, low side out, or something to that effect to minimize interference.
We're talking about a coordinating body that truly believes it rules the world, and they are stuck in the stone age. If they really knew what they were doing, he wouldn't be in this mess in the first place.

Realistically there's no need for a coordinating body any longer. They don't do anything, and the FCC doesn't enforce anything, so what's the point? All told, it just needs to be folks working together to mitigate problems.
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

tvsjr wrote:MtronPTI (previously Piezo) is the recommended model. I've had good luck with the 4133C: http://www.mtronpti.com/resources/2133- ... 2013-07-19

That said, Chris is right. These filters are about as tight as you'll find, and they are only 20dB down at +/- 30KHz. 50KHz for 40db. At 15KHz, you'd be lucky for 10dB. And these filters aren't cheap... $600 or so, if memory serves.

You need to work with the other repeater owner and your coordination body and move. Alternatively, I suppose you could operate reverse split. I have to wonder who would coordinate an input and an output 15KHz apart...
Not to mention it's going to knock your receiver sensitivity down into nothing, thus requiring a preamp (or a higher gain preamp), and then you've put yourself right back to square one.

Once again, it's not the RF, it's the IF.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

You are all well reasoned and know the players except that it is 147.70 v. 147.090 -- Catalina. The radio techs at County insist that this is the solution and that a proper preamp will bring it back up. Perhaps changing the IF filter to 15KHz will help.

Dammit! :x
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

I would take a look at Catalina's output and make sure there isn't excessive deviation going on there, causing splatter into your receiver. It's not a very well known fact, but in the case of 15kHz repeater spacing, the repeater's transmitter should be WELL below 5kHz. A lot of folks seem to think that you set the transmitter deviation for 5kHz and you're done. Not anymore.

Check this link: http://www.tasma.org/coordination/standards/ That's the technical standards for TASMA. Note that they want maximum deviation of 4.2kHz peak. With regards to the repeater receiver, essentially, TASMA is saying that you need to narrowband your repeater's receiver using the COM-SPEC filter kits that are easily available in order to make it work with the 15kHz spacing. THAT will DEFINITELY have a positive effect on the problem. The other half of the coin is that Catalina needs to make sure they are adhering to the 3kHz. The drawback is that users with "ham" radios that are so typically well above 5kHz deviation from the factory will likely sound crunchy into the repeater receiver.

Too many people don't know/read the TASMA technical standards, so they end up with this problem. I'm not saying that you didn't read it, but it's easy to forget that 5kHz is essentially a thing of the past. If everybody tightens their receiver IF and dials down their transmitter deviation, it'll work. No, I don't like it either, but you can thank TASMA for it's lack of foresight and "amateur" technical committee for coming up with ridiculous frequency spacing.

Regardless, 15kHz is just grossly incompatible with today's "junk" amateur transceivers. Works great with commercial rigs, but not with ham stuff.

Unfortunately a crystal filter just isn't going to do anything for you, Bob. They're damned expensive, and when they work, they work WELL and are worth the money, but they require a preamplifier (generally) to recover the losses into the receiver, and most importantly, they just aren't 15kHz tight.

In this case, I suggest using the system and filing a complaint with TASMA. They made this bed that is 15kHz, so perhaps it's time for you to tell them they need to change the sheets.

I guarantee Catalina isn't going to move. It's been there since dirt was invented. BUT - if the above suggestions don't work, they may be able to find you a more suitable pair. Work the system.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Thanks, Chris. It helps that you know the players and the rules. This issue has existed since 2009 and complaints only caused me to be covered with crap. It was a huge mess trying to get a dinosaur repeater to understand that they may have run all previous tenants of 147.705 off but I am not leaving.

Ironically, Catalina uses the same equipment that we used: A TKR-750, a 180 watt amp (that we DON'T use), and a DB224 antenna aimed into the Los Angeles basin azimuth 50 degrees, and a RC-210 controller. We aimed at azimuth 230, Huntington Beach from San Bernardino.

We started with a Kenwood TKR-750, which is a wonderfully simple repeater with good audio and very capable with a RC-210 controller. Its drawback is its selectivity is only 60dB at 6KHz. I still own two but long ago switched to the Moto MSF 5000's as a partial solution. I own three that we intend to link via Allstar. For several years Catalina hasn't been an issue. But it means running a tighter squelch and missing out on distant traffic. We have kept our deviation at 4KHz while Catalina has kept their deviation at 4.2KHz meeting TASMA's requirement. BUT -- the TKR-750's are notorious for not throttling the deviation. One can yell into the mid and force the TKR-750 to go wide. Keller has the same issue. Don't even think of using a preamp following a Chip Angle band pass cavity set with a 1MHz window that is 90dB down. Awesome. But that means 3dB loss and then the duplexer. Catalina is only 15KHz away and the Chip Angle is useless.

Our only recent change is that we tuned the MSF 5000 exactly to the Motorola instructions and achieved a wonderful .18uV sensitivity. Weak signals can be heard quite well. HT's from 80-100 miles away easily get into our machine located on Heaps Peak in the San Bernardino National Forest 120 miles away from Catalina. But with their antenna aimed at us with 180 watts behind it the predictable over-deviated mobiles that can easily be heard on my own commercial equipment from Running Springs end up on our repeater input riding the coat tails of our weaker signals. Using the peak/hold feature on my service monitor I kept track of Catalina and they denied an increased deviation laughingly telling me that I had no clue. Peak/hold? It doesn't exist. Sure it does on a HP Agilent 8924c.

In absolute fairness to Catalina their 180 watt output isn't the problem. It's more the use of a TKR-750 that can be over-deviated by hams that run simplex and think that pumping up their audio will give them more range. Catalina actually used this as their justification for not dialing their deviation back from 8KHz. We insisted and TASMA/FCC ordered it so. But as I said I ticked off a lot of hams. It has affected our user base and caused many hams seeking a pair to use our legal moves against TASMA. This ticked off TASMA and several board members had to resign to protect their security clearances. But the new technical committee IS trying to correct prior foolish decisions and I publicly compliment Chuck, Sean and the rest of the committee.

For the readers you now have an idea of the political landscape. If you are a 50 year old repeater the new guy will get hosed even if coordinated and in compliance with both TASMA and FCC regulations. One might think that by allowing their deviation to go wacky Catalina is creating intentional interference. But welcome to the real world where we really just need to get along. Catalina HAS tried. The real issue is the 15KHz spacing and the inverted pair created by TASMA. The national pair is 147.105+ and not 147.705-. This places Catalina's output on our input and vice versa. I can't count how many times I heard Catalina users *itching about our interference to them without understanding the regular interference to us.

So let's move forward. The MSF 5000 is an excellent repeater. The receiver is tuned right on and our 6,400 foot elevation gives us tremendous coverage. Our back-up location uses a 9dB cardioid pattern DB224 antenna while our commercial site uses a Commander Tech Station Master with 5.25dB of omni directional gain. We cover all of metro so. California AND the high desert. But how do we resolve the interference? Do we use narrowband on receive using 15KHz Com-Spec boards? Commercial radios are great. I own and use Motorola's almost exclusively. One can program them for 2.5, 4, and 5KHz deviation. But that doesn't solve the issue of, say a Yaesu VX7 HT that has loud audio and I need to use "half-deviation" so that I sound good into my own repeater. Even my Bendix-King fire department radio sounds fantastic!

There are no more pairs... I am a nice guy that wants a professional quality repeater and good users. But I cannot create another pair. As a true ECOMM repeater dedicated to emergency communications and paying for three commercial sites so that HT's can be reliably heard I cannot deal with a repeater's output on my input. ECS, ARES, SAR and even unaffiliated hams calling for help where a cellphone doesn't work we are forced to deafen our own repeaters to minimize interference.

147.705- 167.9
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

Put the narrowband IF filters in.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

I have ordered the 15KHz kit.

I apologize for hijacking my own thread. After your comments re: TASMA I thought that the readers would benefit from knowing the true story of what has transpired and perhaps relate it to their own experiences, past, present or future. I also wanted to be on record that Catalina has tried to cooperate as well as TASMA has a new board that is also trying to remedy prior inconsistency. Too many harmful words have already been said and sniping at and blaming again will only rekindle and inflame the issue once again.

I will report our experience once the 15KHz kit has been installed.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

No worries. Those who know TASMA know the nightmare.

Let us know how the filters work out. If TASMA has users that routinely peak out of their repeater and into your receiver, they need to dial their deviation back to 3kHz. It's only fair to be a good neighbor (them being a good neighbor to you).
User avatar
escomm
Queue Moderator
Posts: 5170
Joined: Fri Mar 24, 2006 8:24 pm

Re: Adding a Piezo Quartz Filter

Post by escomm »

At least SCRRBA appears to have obtained a rope in attempt to cure their crainius rectitus..................
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

LOL.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
MSS-Dave
Posts: 770
Joined: Mon Jun 30, 2003 6:02 pm
What radios do you own?: XTL5K, NX300, PD782, Spark Gap

Re: Adding a Piezo Quartz Filter

Post by MSS-Dave »

I would take a look at Catalina's output and make sure there isn't excessive deviation going on there, causing splatter into your receiver. It's not a very well known fact, but in the case of 15kHz repeater spacing, the repeater's transmitter should be WELL below 5kHz. A lot of folks seem to think that you set the transmitter deviation for 5kHz and you're done. Not anymore.
I'd also hope that they are running their TX through a circulator and a cavity before a duplexer just to clean up broadband noise. Granted, 15 kHz is TOO tight for what is going on out there and that extra filtering may not make any difference but it's good housekeeping IMHO.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Well, we got the 15KHz rocks installed and so far so good. Audio quality remains excellent, as does receive. We're still getting a usable signal down deep and can now use the Angle Linear cavities and the 17dB preamp. Before you freak out -- I added a 10dB attenuator so actual gain is 1-3dB. Too tired to measure the duplexer and Angle Linear loss in dB and assumed 3dB each yielding about 1dB net gain or so. No Catalina when injecting a 3x1 signal until about 8KHz deviation. An OTA signal I caught suggested noise from something but it wasn't Catalina and only happened once without really harming the weak signal.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

Glad it worked out!
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Hardly success. Our repeater sounds like crap. The audio is terrible and stations are breaking up sounding like they are deviating out. They switched to another repeater and sound fine. We may have to put the old filters back in and increase our squelch so only stronger signals can get into the repeater. I'm pretty pissed. A squelch tail that was never there before maintenance and piss poor audio now that the filters have been changed. My Tech. Chairman refuses to accept that we cannot run a preamp, attenuator or not, especially right next to a major site with high power transmitters. The Angle Linear should trap out what doesn't belong. But who cares about an increase in the noise floor by using a preamp. Anything to hear a HT 76 miles away whose user complains about the repeater anyway and no matter what. Too many changes instead of making one change at a time and hearing the results.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
Jim202
Posts: 3609
Joined: Sun Sep 09, 2001 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by Jim202 »

What your hearing is typical of many ham radios out there. The deviation is not set correctly in them. The real solution is to have a tech meeting and set up a service monitor so that the individual user radios can be have the deviation set to where they should be. I would try and work with the users that are breaking up the most as the first ones to have their radios looked at.

I have been involved with a number of clubs that have set up a couple of Saturday meetings to be able to test each users radios. The major drawback is the process is slow and requires that the individual radios be opened up and have the service manual available to locate the deviation adjustment pot to be able to turn down the deviation to where it should be. It might take as long as 15 to 20 minutes to set up, open the radio, make the adjustment and close the radio back up. This also means that you need to have a DC power source and a power cable available for all the different makes of radios your going to be playing with.

This all will take some careful planning and some logistic material to be available. Don't forget a full electronics tool kit to get into some of these radios. Also need a table or bench to work on. But when it's all said and done with, there will be a number of comments that indicate how much better everyone's audio sounds.

We have found that the majority of the off shore radios have high deviation settings right out of the plant or origin. In many cases, I don't think they even took the time to measure it.

It will take persistence and everyone to lend a hand and help. The biggest problem will be trying to get everyone lined up to get their radios bench tested. You will be surprised how many of them will also be off frequency. This won't all be accomplished in one day. The larger the user base, the longer it will take to go through each and every radio.

Be patient and work through this. It can and will get better.

Jim
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Jim,

Frankly, NO. We will not get into users radios and set our selves up for complaints of radios that no longer work. We will NOT attempt to get into itty bitty Baufeng radios or even Yaesu, Icom or Kenwood. "You broke the case on my radio. It was PERFECT before you touched it. Now it doesn't transmit well!" "Please define transmit well..." "You suck! Your repeater sucks! I am going to sue you." And so they shall and so shall they will likely win. The burden of proof will be on us in spite of the law stating otherwise.

This issue is about TASMA and 15KHz spacing when TASMA knows that radios are designed for 20/25KHz spacing.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

+1 what Jim said.

If the rptr tested good after the filters were installed, but some of the users sound bad, it's the users. GIGO (garbage in, garbage out). We ran into this during narrowbanding. People clicked the 12.5khz button and programmed the radio, but they didn't check it on a service monitor. Sounded horrible afterwards especially after we did the repeater.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Gentlemen, this is ham radio and not commercial. The MSF 5000 has (had) excellent audio. Ham radios are designed for 20/25KHz spacing and not 12.5KHz. But because a frequency coordinator chose to squeeze in repeaters by using 15KHz spacing and a reversed pair assignment we have to jump through hoops? I regret that neither of you read all of the facts. TASMA reversed the pair and put the output of anther repeater within 15KHz of our input. The national pair is 147.105/.705. So then why reverse the pair that has TWO repeaters outputs on its input. 147.090 and 147.120 are the outputs on our input of 147.105. See the real problem? Because our prior repeater tech cranked up the squelch we did not notice the problem until he was replaced and maintenance done. One the squelch was dropped we suddenly heard the problem.

The problem is not technical. It is regulatory. TASMA cannot affect radios from any manufacturer. Admittedly some crank the deviation up but based on 20/25KHz standards. Please don't blame the users for a problem created by a frequency coordinator.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
escomm
Queue Moderator
Posts: 5170
Joined: Fri Mar 24, 2006 8:24 pm

Re: Adding a Piezo Quartz Filter

Post by escomm »

Nobody is blaming the users. They're blaming their radios. Anyhow, with comments like the ones you've made, I think it's safe to say you've just about reached the conclusion of your efforts here to settle this problem. Best of luck sorting this out with TASMA.
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

krazybob wrote:Gentlemen, this is ham radio and not commercial. The MSF 5000 has (had) excellent audio. Ham radios are designed for 20/25KHz spacing and not 12.5KHz. But because a frequency coordinator chose to squeeze in repeaters by using 15KHz spacing and a reversed pair assignment we have to jump through hoops? I regret that neither of you read all of the facts. TASMA reversed the pair and put the output of anther repeater within 15KHz of our input. The national pair is 147.105/.705. So then why reverse the pair that has TWO repeaters outputs on its input. 147.090 and 147.120 are the outputs on our input of 147.105. See the real problem? Because our prior repeater tech cranked up the squelch we did not notice the problem until he was replaced and maintenance done. One the squelch was dropped we suddenly heard the problem.

The problem is not technical. It is regulatory. TASMA cannot affect radios from any manufacturer. Admittedly some crank the deviation up but based on 20/25KHz standards. Please don't blame the users for a problem created by a frequency coordinator.
Oh no. I read your problems, and understand the subject matter. You essentially have a narrowbanded system now with NB problems. With a 15khz filter on the front end of a system designed to use +/-5Khz of deviation, 10khz is occupied by voice with (less than) 2.5khz of guard band on each side. The users have to be perfectly centered, and their deviation has to never exceed the max, or they will sound terrible. Period. Your repeater will work fine for people who keep their equipment in good working order, and you can tell immediately who doesn't. It's kind of sweet actually. Look at the bright side - You have a chaff sifter.
User avatar
d119
Posts: 3532
Joined: Tue Mar 19, 2002 4:00 pm

Re: Adding a Piezo Quartz Filter

Post by d119 »

Bob, the other option is to flip your pair as well, and tell TASMA to deal with it... ;) They are a "coordinating body", not a law enforcement agency.

Unfortunately the 15kHz thing is hardly the norm in amateur radio in general, and as such, most peoples radios are set up for 20/25kHz spacing at 4.5-5kHz deviation. Just doesn't work in a 15kHz environment. Commercial gear would sound great, but as you said, this is amateur radio and not commercial radio.

The other thought is this - a lot of the NEWER amateur gear has a WIDE/NARROW setting that can be programmed per channel - you could encourage your users with this capability to set their equipment for NARROW mode, and that would clean quite a bit of it up. I know most of the stuff manufactured in the last 5-10 years has this setting. Unfortunately it doesn't work in the commercial world due to the radio not having a switchable RX IF, but in this particular case, it would work since we're concerned about the repeater receiver, not the users receiver.

Not all of 2m in SoCal is 15kHz spacing, just certain sections. You could petition TASMA for another pair...
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

You're right on the money, Chris. I emailed Chuck last night and asked that our pair be flipped. He stated that they would have to look at the ramifications but I asserted myself. In absolute fairness, Chuck, Sean and the rest of the new committee are working hard to correct what they can. I have no quarrel with any of them.

We have noted a major difference with our repeater and it appears that changing the crystals requires a tune-up afterward. Users are weak and often cannot break squelch. Taking out the crystals destroys them and we're lucky to have a third MSF for parts. It's a shame because it is a fully functional MSG :-(

This was a mistake. The only solution as I see it is a reversal of the pair, especially since our plan has always been a machine on Sunset, Quartzite and Heaps Peak (where we are now.) All will be linked with Allstar. We're already on node 41660 but our repeater sounds so bad now that we've made the switch. The Wide/Narrow settings on ham gear basically just decreases the deviation and still leaves the receiver at 20/25KHz. We only wasted $30 and they don't have 20KKHz rocks even as special order.

147.090 ==> 147.690
147.105 ==> 147.705
147.120 ==> 147.720

TASMA needs to think abut this.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

AFTERMATH: After installing the narrow banding kit recommended by TASMA and experiencing very negative results we removed the board today and installed a replacement instead of unsoldering the crystals. We do not fault TASMA at all and understand that they are doing their best with people that spend far too much time complaining. As volunteers they are under appreciated.

It should be noted that if one narrow bands one needs to expect a reduction in audio, and a reduction in service area by about 30%. This week we experienced both. After changing the board back we recovered our lost audio, and our massive coverage area.

We learned a lot.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
kcbooboo
Batboard $upporter
Posts: 2117
Joined: Wed May 01, 2002 9:03 am

Re: Adding a Piezo Quartz Filter

Post by kcbooboo »

Usually some resistors need to be changed to compensate for the decrease in audio that goes along with narrowbanding. There are several dozen parts that change between a Uniboard built for VHF/UHF/800 (5 kHz)and one built for 900 (2.5 kHz) besides the HearClear circuitry (and its jumpers) that's present on the 900 MHz Uniboard.

You can easily decrease the TX deviation, but there's no adjustment for the reduced RX audio, and that will affect the squelch as well, requiring you to increase the EEPot values to compensate.

Bob M.
User avatar
escomm
Queue Moderator
Posts: 5170
Joined: Fri Mar 24, 2006 8:24 pm

Re: Adding a Piezo Quartz Filter

Post by escomm »

krazybob wrote:It should be noted that if one narrow bands one needs to expect a reduction in audio, and a reduction in service area by about 30%.
Your users need to have their equipment put on a service monitor and get a proper alignment
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

escomm wrote:
krazybob wrote:It should be noted that if one narrow bands one needs to expect a reduction in audio, and a reduction in service area by about 30%.
Your users need to have their equipment put on a service monitor and get a proper alignment
+1

And I'm not rehashing my views on lost range simply because of narrowbanding.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

Then you will like this, Bill ;-)

It is interesting that after changing the main board our receive increased considerably. Odd. Really odd. But with that said we can get the squelch to open at .225uV although a 1KHz tone could be heard down to .17uV. This is after the duplexer and Angle Linear dual band pass cavities. We may add the 17dB preamp back in but with a 14dB attenuator. Hardly seems worth it to get back 3dB loss. It strikes me that people throw around numbers like ".15uV sensitivity" but that isn't real life. At what dBm or uV level can they get a workable signal that may not be 12dB SINAD is what matters. At any rate this main board just popped in and did not require any tune-up.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
tvsjr
Posts: 4118
Joined: Fri Nov 28, 2003 9:46 am

Re: Adding a Piezo Quartz Filter

Post by tvsjr »

escomm wrote:
krazybob wrote:It should be noted that if one narrow bands one needs to expect a reduction in audio, and a reduction in service area by about 30%.
Your users need to have their equipment put on a service monitor and get a proper alignment
You're suggesting average hambones get their equipment aligned? As long as it's +/- 2KHz and deviates somewhere between 4 and 8, that's good, right?
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

tvsjr wrote:
escomm wrote:
krazybob wrote:It should be noted that if one narrow bands one needs to expect a reduction in audio, and a reduction in service area by about 30%.
Your users need to have their equipment put on a service monitor and get a proper alignment
You're suggesting average hambones get their equipment aligned? As long as it's +/- 2KHz and deviates somewhere between 4 and 8, that's good, right?
Or so. Roger that.
krazybob
Posts: 107
Joined: Tue Jul 26, 2011 2:29 am

Re: Adding a Piezo Quartz Filter

Post by krazybob »

tvsjr wrote:You're suggesting average hambones get their equipment aligned? As long as it's +/- 2KHz and deviates somewhere between 4 and 8, that's good, right?
As Bill accurately writes -- and we did not think this through enough -- when you narrow band you have to control the input or the users will "dev out." Yes, they sure will. Kenwood TKR-750's are known for this but can be switched to 12.5KHz with a menu option but still transmit wide because you set the deviation. That's why we switched to a MSF. We did not think that 15KHz would be quite as bad and pulled the trigger. We have since located 20KHz crystal!!! We will need to see a pass band chart first but it is a toss up between 12.5KHz and 25KHz. Equipment used by most repeaters as you know was designed for 20/25KHz. Ham equipment accordingly is sent out often adjusted for the median - 8KHzish. When I said that we were not going to have a tuning party I meant it based on a sue-happy country that we live in.

We hope that the 20KHz play nicer.
Bob - AF6D
__________________
FF EMT IS-400 Certified
AF6D Amateur Extra Class K6ECS Trustee
So. Calif. Emergency Comm. Service Group
147.705(-) 167.9
User avatar
Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Adding a Piezo Quartz Filter

Post by Bill_G »

krazybob wrote:As Bill accurately writes -- and we did not think this through enough -- when you narrow band you have to control the input or the users will "dev out."
Yer welcome.

I learned a long time ago how to earball a rcvr in by over deviating. It was especially useful for models with tunable IF stages. They had tighter skirts, but weren't perfectly linear. Max signal at the det wasn't always the least distorted, or the best sensitivity. I could quickly dial a rcvr in, or ferret out a failed stage, without a metering panel. Later on, when NB'ing was in full swing, you could easily tell which radios had been missed (or needed further attention) in the fleet by listening to the channel. And there was always one or two or three.
User avatar
escomm
Queue Moderator
Posts: 5170
Joined: Fri Mar 24, 2006 8:24 pm

Re: Adding a Piezo Quartz Filter

Post by escomm »

Boy all these "problems" with the "repeater" and not only have they not bench checked their subscriber but actively refuse to do so?

You can lead a horse to water.............
Post Reply

Return to “Base Stations, Repeaters, General Infrastructure”