VHF MSF5000 Alignment Questions

Big Towers · Post by **Big Towers** » Fri Oct 17, 2003 3:00 pm

Hello all. Well, I finally purchased my first VHF MSF, a C73CXB-7106. I have worked on UHF MSFs for many years, but never even so much as peaked at a VHF. So, now that it is here, I need to tune it up. Anybody have a quick alignment steps for the receiver. The transmitter seems to work fine already. It was moved in freq. VCO settings would be good as well, don't know it they were set. I have the software and digital test sets, just haven't found a "deal" yet on a VHF manual. A part number would be good for that as well, may have to order one.

Thanks,

bernie · Post by **bernie** » Fri Oct 17, 2003 11:35 pm

My two bits worth:
You don't have to worry about tuning the VCO.
You can't, they are not adjustable. They look like they were borrowed from an MCX100
The alignment is exactly the same as the other bands, paradoxically, the receiver front end is smaller than the 800Meg model.
As I recall, you have to remove the front panel to get at the pre-selector.
The manual: 68P81082E20

Big Towers · Post by **Big Towers** » Sun Oct 19, 2003 2:02 pm

Thanks Bernie,
I thought there had to be a "front end" on the thing. And sure enough, tuned up just like a UHF. Receiver at about .2uv so everything seems fine.

kcbooboo · Post by **kcbooboo** » Mon Oct 20, 2003 10:15 am

Beware of the dreaded "whiskers" that seem to form in the silver-tinned front ends and VCOs of MSF5000-series RF trays. 0.2 uV sensitivity may sound good, but the radio should break squelch at around 0.1 uV. Anything higher and you may have some miniscule whiskers growing inside the various RF sections. When they get long enough and short things out, your receiver will become quite insensitive or not tune at all.

I think you can search for whiskers and find another thread all about them.

Bob M.

Big Towers · Post by **Big Towers** » Mon Oct 20, 2003 1:44 pm

Thanks, I have read about them before. This one will open squelch below .1, just move the IFR off the stop and it starts cracking. Ordered a manual today so will be better able to see what I am doing. I had a few odd things, like the repeater would key with carrier squelch signal, but would not stay keyed. I re-did some of the programming and it now seems to work right, but using "SC (Signal and Code)" on receiver and repeater settings would allow the thing to key with carrier?? Putting it in C only solved the problem, but, may leave my radio in a less than desirable mode as far as the old "and squelch" is concerned. Will do some more playing when we get ready to put it on the mountain, but for now it seems to work.

Also, this is a C73CXB7106BT. What is the "Moto" power level on this thing. I have seen the standard 110 watts and I have also seen people claiming these to be 150 watt. The fans intrique me as the 110 watt UHF doesn't have fans. If these are 110 watt VHF, what is so badly done that they felt they needed fans. I would think a 110 wat VHF would be easier to make efficient than a UHF? If they are 150 watt then there would be an explanation, but unsure.

kcbooboo · Post by **kcbooboo** » Mon Oct 20, 2003 1:49 pm

Typically the 7 means around 120 watts. My C64 UHF model does NOT have a fan but for some reason the high power units do. High in this case usually means 250 or 350 watts, and they use two power supplies and two power amplifiers to get it that high with some form of combiner.

I find that the power amp does generate some warmth when it's been on for half an hour or so, and I intend to put in a small fan just to stir the air up a bit. It probably won't hurt the radio but I know I'LL feel a lot better.

Bob M.

Post by **batdude** » Mon Oct 20, 2003 2:37 pm

the pa is rated at 125w in the C73 series.

the C93 is a whopping 350w.... i have one if anyone feels brave (and has one hello f a set of duplexers)

doug

Big Towers · Post by **Big Towers** » Mon Oct 20, 2003 6:33 pm

That is interesting. I have a half dozen or so of the C74s at "110 watts" and the C64 is a 75 watt. None have fans. The C94s on the other hand do, and not much of a surprise there.

The part that makes me wonder is why a VHF station at virtually the same output "needs" fans when UHFs don't seem to. Is the 15 extra watts on a 125 watt VHF MSF that much different than a UHF. Based on all previous designs, VHF usually is not as heat generating as a UHF of the same output and design.

Just wondering if there was some secret reason, you know, payoff from the power companies, something!

bernie · Post by **bernie** » Mon Oct 20, 2003 7:50 pm

My two bits worth:
Power settings & fans.

Just because it may be possible to set the power control far in excess of the recommended values does not necessarily mean thet the station will operate in any and all conditions that way.

I have seen several cases in the 800 trunking stations where a tech had an out of cal wattmeter, and was actually setting the power to 90w or so.
The result was that the station would go into TIB fail due to power cut back when the critter got really hot, only to cool and work when the tech got to the site, and seemed to work properly.

Cooling fans.
When you are operating the PA at full power continuously, such as a control station on Motorola trunking, paging, or whatever the PA will get really hot, and will likely fail in time if not kept at a reasonable temperature.
The fan kit is an option on most stations.
Fans are way cheaper than service calls.

Programming.
Default has the repeater key with carrier & PL, holds with PL.
the receiver is PL only. "S=squelch, C=coded"
In my experience this works fine.

Whiskers in filters issue.
This usuially shows up as low, or missing receive meter 3.

I would not be too concerned about opening the squelch at .1uv because the site noise is very likely much more than this.

I prefer to use SINAD to measure sensitivity.

Have fun!

kcbooboo · Post by **kcbooboo** » Tue Oct 21, 2003 5:25 am

Sorry, I should have qualified that 0.1 uV squelch opening threshold by adding "on the bench with a signal generator". I would not recommend leaving the squelch set at the threshold no matter where it is or will be.

I've been wondering about those repeater and receiver settings. In my own case I have an MSF5000 set up as an amateur repeater with an external controller. I only want incoming signals with PL to open the receiver or be allowed to key the repeater. However, once the system is repeating, there's no need for PL, so ordinary carrier squelch will do. I think I have my system set for PL only to open things up, then PL and carrier to keep it on.

In this situation, what do the receiver qualifications do for me if left in CSQ mode vs PL mode? Similarly, what do the repeater qualifications do for me? I am NOT using the built-in repeater controller but I am taking audio out of the MRTI connector and getting other signals elsewhere.

Bob M.

Big Towers · Post by **Big Towers** » Tue Oct 21, 2003 8:19 am

Bob,

My experience with UHF Analog MSFs are that I prefer the SC coding versus other methods. The reason I care, which may be lame, is that in the SC mode, the repeater acts like an old Micor with AND SQUELCH settings. What this really means? The "Jap Tracs" on the system that do not have reverse burst will still generate a quick "pop" when unkeying versus a long annoying squelch tail like some old motrac opr something. However, the SC settings all around on this particular MSF was generating a long annoying squelch tail. If I remember right, the "receiver" setup using SC should do what I want, it would close the squelch at loss of PL as well as signal. The repeater activate settings should be less critical except that in a repeat activate set at SC and repeater hold at S, once the repeater is keyed by someone with PL, then anything can keep it keyed up (intermod). I didn't spend a lot of time on this yet, but will go back to programming once we are ready to put it on and see if I just wasn't doing something right. I have it set at all Cs right now and it does help on the squelch tail but not sure it is exactly right. If only everybody would use reverse burst radios it wouldn't be an issue. I may have just had the station squelch open and in that case the squelch tail happens regardless if my UHF experience is the same.

bernie · Post by **bernie** » Tue Oct 21, 2003 10:20 am

My two bits worth:
I believe the reason for using "PL" to hold the repeater and receiver has to do with the performance under weak, fluttering signal conditions.

I think that this is why the "Drop out Delay" was invented.

There is no real advantage until the weak signals are present.
In the "old days" when coded squelch was rare one of the main selling features of the repeater was how well the squelch peformed.

When a customer noted the squelch tail, I informed them that was the systems way of indicating "Off brand" radios.
It is there to remind you how much you saved on your radio.
By the way, what else is left out to make your radio cheaper?

On the Analog station if the front panel squelch is open, and the "PL" switch is in monitor, the repeater will send squelch noise during DOD. Not that I have ever done it.

Big Towers · Post by **Big Towers** » Tue Oct 21, 2003 11:55 am

Bernie,

I agree, the ability of PL tone to hold the repeater at weak signals is pretty amazing. Although a squelch can be set on the harry edge to open with unuseable signal, it is not absolutely stable. I have seen many repeaters key at no squelch opening by detecting the faintest of Sub audible tone and it will definately keep things keyed when squelch (signal) alone won't do it.

I know that the station squelch does affect the closing of the squelch on input drop on the analog stations so I may have not looked at that when I was experiencing the wierd response. Will look at it more carefully when I get a chance.

I quess the "Cheap Radio" detector is one way to look at it, but those of us using not so cheap would just as soon not have to know:)

Post by **batdude** » Tue Oct 21, 2003 2:31 pm

then i wonder why my analog uhf msf (in ham service) has the nastiest squelch crash i have EVER heard (on non reverse burst radios ONLY)

all of my settings are "SC"....

hmmm

doug

Big Towers · Post by **Big Towers** » Tue Oct 21, 2003 3:31 pm

Doug, I don't know. Is the manual squelch control closed enough that when in PL disable the squelch is closed? That may be part of it, I seem to remember our getting long tails and finding that the squelch was actually open.

All of ours are SC on Rpt Act, Rpt Hold, and RX audio and we have 4 of them on Ham service that sound great. Thats why I think the same thing may have been what was happening with the VHF. Otherwise, changing everything to C will certainly make it better but not the best way. That would be my first check, and also that the repeater squelch is also closed. Need a digital test set to check that real easy but it seems that will also cause a problem in that it takes awhile for the PL decoder to shut off the audio path and if a squelch is open, that could be it.

I have a UHF analog sitting in the garage ready to go that is working correctly with the above settings. I will try tomorrow to set the squelchs open and see what happens, find out once and for all.

kcbooboo · Post by **kcbooboo** » Thu Oct 23, 2003 5:38 am

My UHF MSF5000 also has a very long squelch crash when keyed by a non-/\/\ radio. I haven't programmed any /\/\ equipment to key it up and make sure the tail is inaudible yet. The repeater squelch is set to 99, but I don't recall what the receiver squelch is set to. As I'm not using the built-in controller to run the repeater, that setting probably has no effect. In fact, at one time when I was working on the interface, the only way I could get an open squelch noise was by disabling the PL and using the front panel SQ control. The EEPOT squelch settings would never open the squelch, Maybe I need to remove the PL qualifier via RSS before setting the squelch.

I'm sure that the PL decode circuitry and the microprocessor are what's keeping the receiver open for such a long time. I can change the circuitry but not the way /\/\ programmed the micro.

Bob M.

Big Towers · Post by **Big Towers** » Thu Oct 23, 2003 2:33 pm

Bob,

I know that several of the ham" controllers and even some of the commercial multi tone panels use discriminator "unsquelched" audio in and some are not good about "squelching". Many are really good and sound better than reverse burst, no noticeable noise at all, but I think some of those use a audio delay factor as well.

However, here is the results of my test on an analog UHF using a YeaZoo VX5 with no reverse burst.

Repeater is programmed fo SC on RPT ACT, RPT HOLD, and RX Audio.

When turning the manual station squelch (the knob on front) down so as to be open, even with PL Enabled (Looking for LED on digital test set indicationg R1 squelch open, I get a long squelch tail when unkeying the VX5R and no squelch tail when unkeying an MTS2000.

Putting the manual squelch back so the LED extinguishes, back to a fast pop or the slightest of squelch burst. Next I open the Repeater squelch, again using the LED on the test set to tell me when it was open. Unkeyed the VX5 and no change in squelch tail, still remained fast with just a pop.

So as I expected, it is probably the station squelch not also being set that is causing the long burst on non reverse burst radios. With PL stations, you don't know if that squelch is closed unless you have a test set plugged in AND the PL disable switch on so may well be left open.

I need to plug my computer back into my digital VHF and try some differnt settings on it to see what it does.

kcbooboo · Post by **kcbooboo** » Thu Oct 23, 2003 2:54 pm

I am NOT using the MSF5000 controller as a repeater controller. I am picking up receive audio from the MRTI connector, the MRTI is enabled, and there are two signals available on the TTRC board that give me RStat and RxStat, or something like that. I believe one or both of these also comes out the system/option connector on the side. One seems to react to any input signal, the other only moves when that signal has PL. Both of these are going into my CAT200 repeater controller: the first as a COR signal, the second as a PL signal.

I don't think that the front panel squelch has any effect on this setup; I think it's just for the front panel control jack (handset or local speaker). Now, like Nand, I could be wrong ! I do know that the squelch burst I hear inside on my tone remote control is extremely long on a non-Motorola radio with PL, yet the burst is only a few hundred milliseconds long when the repeater controller hears it. By the way, I am running an audio delay board in the controller and I've adjusted the delay time to get rid of most of the squelch burst. It could be set to 200 or 256 mSec right now, which isn't too bad. But my MaxTrac repeater has only 128 mSec of audio delay to get rid of the squelch burst.

I'll have to check the other squelch pot settings. Might as well throw them all the way to 99 and see if it makes any difference.

Thanks for the test. I'll have to do something along those lines myself as I do have the digital metering panel and can see things happening. It does mean dragging the tone remote out to the garage where the radio is (I know, times are tough).

Bob M.

VHF MSF5000 Alignment Questions

VHF MSF5000 Alignment Questions

vhf msf

hmmm