Batboard

We have lots of R1225's with 100w TPL repeater AMPS. The problem is to get 100w out, the R1225 have to be run at almost full power. R1225's are not rated for continous (mispelled) duty at full power. Now, TPL makes a repeater amp that will take 10w in and put out 100w, but the current R1225's that we have are not supposed to go below like 15-20w or they will put out spurs and/or become unstable. Could we just put a 3db attenuator on the tx cable before it goes into the TPL to bring it down to 10w? I know the short version is to get better quality repeaters, but the boss like to spend $10 to save 10 cents. Sorry for the long post, FatBoy.

Hi:

1. The Spurious radiation is going to be
alot worse with the use of the 100 Watt Solid
State PA than the Tx section of the radio.
============================================

In general, if you desire " Continious Duty"
( heavy duty ) repeater service, you really
should consider a 100 Watt Micor, MSF5000, something along those lines.

Reason being is those radios were designed
for the application of Reliable Heavy Duty
Service.

Trying to " Patch " your system together, is not only going to be expensive, but may not
be as reliable as you might desire.

2. You will need a Heavy Duty Power Supply
for the Power Amp which may require 25-30 Amps of Continious duty service.

3. You will also need some Cooling Fans not
only for the PA, but the TX Heatsink in the R1225 as well.

4. You can " Easily " reduce the Power in the
R1225's to 10 Watts without Fear of any problems.

( So if you find a 10 Watt in / 100 Watt out
Amp ) you should be OK. I also would recomend
a Cavity Filter between the Tx Exciter & input to the Amp. )

5. You may wish to consider the use of a
Commerical Grade T-1504 Band/Pass-Band/Reject
Duplexer to provide Extra Filtering, and the
use of a single antenna.

6. The Use of Double-Shielded RG-142B/U or
Better Cable is a MUST !!

7. So long as you follow proper proceedures
in the set up process, you may only encounter
minor problems to overcome such as " Noise" which can be generated by the PA, and RF Leakage ( in & around ) the TX Section which
could have a impact on the " Receiver" performance...

Please keep in mind, the " Receivers" in these small repeaters do not have anywhere
near the isolation capabilities compared to
a Micor or Qunitar / MSF5000 Series repeaters.

Most Repeaters have large Cavity Filters ahead of the 1st RF Amp in the Receiver, and
helps reduce RF Noise from affecting the receiver.

Low Power Systems are " Easy" to address, however, when you get into 75-100Watt Systems
many other factors must be considered.

Anyhow, hope some of the information helps.

Monty

Monty,
You make many fine points. However, we have four sites that run LTR. Also, we have many customers that run conv. systems like the above.All of our LTR sites run 100w amps (anywhere from 5-15chs each). If it was my decision, it would be mtr2000's or equiv, cont. duty. But, like I said, the boss will spend $100 to save $1. I was told my Mot that reducing the R1225 (25-40w version) to 10w was not recommended. I will get with my supervisor on monday and recommend we turn it down. I dont know if we can take it that low in the software, again, will check on Mon. Thanks for the recommendations, FatBoy.

1. The Spurious radiation is going to be
alot worse with the use of the 100 Watt Solid
State PA than the Tx section of the radio.
============================================

In general, if you desire " Continious Duty"
( heavy duty ) repeater service, you really
should consider a 100 Watt Micor, MSF5000, something along those lines.

Reason being is those radios were designed
for the application of Reliable Heavy Duty
Service.

I AGREE TOTALLY, BUT THE BOSS WANTS SOMETHING FOR NOTHING. HE IS NOT THE ONE WHO HAS TO TRAVEL TO THE SITES AND SWITCH OUT THR REPEATERS, "OUT OF SITE, OUT OF MIND".

Trying to " Patch " your system together, is not only going to be expensive, but may not
be as reliable as you might desire.

AGAIN, I AGREE TOTALLY. SAVE MONEY IN THE LONG RUN.

2. You will need a Heavy Duty Power Supply
for the Power Amp which may require 25-30 Amps of Continious duty service.

DURACOMS HAVE BEEN THE WAY TO GO FOR US.

3. You will also need some Cooling Fans not
only for the PA, but the TX Heatsink in the R1225 as well.

ONE FACTORY FAN AND ONE ADDITIONAL COMPUTER FAN ADDED FOR FUN (RUDUNDANCY) AGAINST THE BOSS' WISHES

4. You can " Easily " reduce the Power in the
R1225's to 10 Watts without Fear of any problems.

NEWS TO ME, WILL LET YOU KNOW

( So if you find a 10 Watt in / 100 Watt out
Amp ) you should be OK. I also would recomend
a Cavity Filter between the Tx Exciter & input to the Amp. )

HAVENT NEEDED ONE SO FAR. WILL LET YOU KNOW IF I RUN INTO TROUBLE

5. You may wish to consider the use of a
Commerical Grade T-1504 Band/Pass-Band/Reject
Duplexer to provide Extra Filtering, and the
use of a single antenna.

WE USE DB MULTICOUPLERS FOR RX, AND DB COMBINERS OR WHATEVER IS AT THE SITE (WHATEVER WAS THERE WHEN PINN. TOWERS TOOK OVER FROM MOT.)

6. The Use of Double-Shielded RG-142B/U or
Better Cable is a MUST !!

IS LMR-400 ACCEPTABLE? THE SMALL STUFF IS SUCH A PAIN IN THE REAR TO CONNECTORIZE!

7. So long as you follow proper proceedures
in the set up process, you may only encounter
minor problems to overcome such as " Noise" which can be generated by the PA, and RF Leakage ( in & around ) the TX Section which
could have a impact on the " Receiver" performance...

WILL BE ON THE LOOKOUT FOR IT, THANKS AGAIN

Please keep in mind, the " Receivers" in these small repeaters do not have anywhere
near the isolation capabilities compared to
a Micor or Qunitar / MSF5000 Series repeaters.

I AGREE. SWISS CHEESE FOR FRONT ENDS

Most Repeaters have large Cavity Filters ahead of the 1st RF Amp in the Receiver, and
helps reduce RF Noise from affecting the receiver.

HAVENT SEEN THIS AT ANY OF THE SITES I HAVE BEEN TO, CAN YOU ELABORATE ON MODEL NAMES OR DESCRIPTIONS?

Low Power Systems are " Easy" to address, however, when you get into 75-100Watt Systems
many other factors must be considered.

IF I HAVE TO SAY I AGREE AGAIN, I WILL VOMIT (SARCASM). THE EXPERTISE HERE (BATLABS) IS AMAZING
Anyhow, hope some of the information helps.

MORE THAN YOU KNOW

Monty
FatBoy

Sounds like you have quite the situation on your hands. Your systems are busy enough to drive your R1225s beyond their 50% duty cycle, so you need SOMETHING with a better duty cycle. Rather than get the proper gear, your "superior" wants you to Mickey Mouse something, to save a few dollars. You will pay in the long run with that mindset, in set-up time & service calls, but it sounds like you already know that. Sigh...I run into that sometimes as well. It's tough when the real answer is not an option. If it's the customer's equipment, they should be made aware of the pros & cons either way. If it's your own systems which I assume would be running at a profit, the proper upgrade should be done. My two cents...

Todd

Wavtar,
Yes Mickey Mouse it is. It is funny that you said that the best options are out. It seems that he considers all options including doing nothing and then takes the "cheapest" not the most cost-effective.
Also, cannot discount the constant talk of "tightening our belts." My belt is so tight, my head is about to explode. He should have taken his millions he got from N*xT*l and invested it in his business. But, sorry for the rant. Today, he sold all of our "demo" radios. These were radios the shop uses for comms. Now, no comms. I am just glad I go to school for Electrical Engineering. Again, sorry for the rant. Anyone want to compare employees/employers? FatBoy (Loyal employee, Disloyal employeer.)

HI:

As a follow up:

The LMR Series Cable is Ideal too !!

I just prefere RG-142B/U since I have
Type N, Type C, and BNC Connectors that
fit that cable, and its double-shielded, and
silver plated....A little poor on the velocity factors / loss, but the isolation makes up the difference. ( and it works very well up to the 200-250 Watt levels @ UHF Freqs )

I have seen Cheap RG-58/u Melt when 100+ Watts of power is used when/if vswr is
encountered.

With respects to the Solid State Amps, the
addition of a Circulator and
Antenna Combiner is a good idea too.

( However, that can be very costly )

Tech Tip: The Circulators out ouf 100 Watt
Micor Mobiles are super for those PA's that
do not have one.....Solid State PA's make
great intermod mixers.

Hopefully, you are in a area with limited Lighnting problems, otherwise I would strongly urge you you to get as much lighnting protection as possible.

Also, again the " Receivers" in the Maxtrac/Radius Mobiles although are A-OK
for Mobile / Light Duty Repeater Use, they truly have front ends that can be easily
Overloaded either by nearby Transmitters, or
Noise, and that can have a major impact on the Signal to Noise ratios.

Anyhow, the use of a Xtal Filter, Or Broad-Band Cavity / Reject Filter ahead of the Receiver Port can reduce the Noise level and front end overloads thereby increasing receiver performance. Especially helpfull on Mountain Top facilities.

Also, these type receivers due not like
High-Energy Lighnting Spikes....

So, depemding on " your " installation skills, will be directly proportional to
how well your system will work.

You have alot of work ahead of you, and again
be prepared for a host of Minor / Major problems from RF being distributed through-out your system. Grounding will be a very important issue, as well as equipment placement.

Alot of Spare Parts would not be a bad idea
either including PA's and radio replacements.

Saves alot of time when servicing equipment
@ repeater locations.

I have been required to Service alot of similar systems in Mexico....EE Gads, and
its a real hassle ( and expensive )

But as others have said, your boss ( or you )
will pay for it one way or another.

Trying to Reverse Engineer Systems is not very cost effective. But a System Plan is not
a bad idea if everything is considered properly.

======================================
PS: Hams have Modified Motorola UHF Miterks
as a Exciter,( easily Duplexed ) and then used a good Solid State PA for relaiblility, and they have worked very well. They also have a Cast Aluminum Filter Front End too !! ( and are pretty cheap ) as far as Parts are concerned.....Just a small note, and there
are 100's of them in operation....Many are
used in Poor Mans Commerical Service
======================================

Well made " Systems" tend to operate very
well.

MS

<font size=-1>[ This Message was edited by: [email protected] on 2001-12-15 08:22 ]</font>

Seems some "sales person(s)" sold a lot of customers 45 watt R1225s on TWO watt channels in UHF splinter frequecies.
I have and have worked on LOTS of R1225s and the 45 watt UHF CAN be turned down to TWO watts no problem and you get the benifit of the much larger heat sink.
An R1225 turned down CORRECTLY to ten watts should run all day! This involves recalibration of all set points. I usally recheck the transmit on a spectrum analizer, but I have not seen any increase in the spur content.

I had a boss that Mickey moused the same type setup....Had Kenwood TKR820's coupled to TPL AMPS and it never was very reliable.....It seems alot of Two way shop owners are cheap-o's I saw the setup when I visited the site and couldnt believe my eyes..Who ever thought of rigging desktop repeaters to AMP's and selling LTR (which in my opinion is crap anyways)service on UHF.alot of these radio dealers should have minimum requirements to set up a system...Those darn techs were being paged out every week for an AMP going bad...or repeater failing...i wonder why?