Batboard

CAN SOME ONE PLEASE TELL ME IF IF IT POSSIABLE TO TWEAK THE RECEIVE ON RADIUS M100. I PUT TOGETHER A REPEATER AND WANT TO PEAK RECIEVE. DON'T HAVE SERVICE MANUAL.

Yes it is possible, but you'll need a service monitor, dummy load, and lots of other test equipment. You'll also want to tune the antenna for lowest SWR, and you'll need an SWR meter for it also.

It's not as simple as firing up RSS and putting in some mumbers.

You'll probably want a service manual also. Would you try to fix a car without knowing what does what? It's the same thing.

Do you have a duplexer? is this a R.I.C.K. repeater or a hack-job one with the 2 radios connected directly together?

And also, please don't post in caps. Makes your posts hard to read

Thanks for the reply. I have a sevice monitor, dummy load sinad anolog meter, On the Bird watt meter I have a 1.3 swr. I put the repeater together with a R.I.C.K. What I would like to do is tweak the the receive for one freq. Thanks Tom

KE9RY-

I deleted your duplicate thread. Please do not post the same thing multiple times - sometimes, it will take a day or two to get an answer. Be patient... no one here gets paid to answer questions, thus other parts of life take precedence.

Also, 601 is correct - please disable the CAPS LOCK. I see your second post is in proper case... you'll find that posts which are easier to read are read and replied to much more frequently.

Back to your original question - if memory serves, the receiver front-end in a Maxtrac/GM300/M100/etc. is non-tunable. What sort of sensitivity are you seeing now for 12dB SINAD or 20dB quieting?

Also, make sure you observe proper cooling procedures for those radios if being used in a repeater environment. Otherwise, you'll be repairing a toasted RF board due to excessive heat.

"...What I would like to do is tweak the the receive for one freq...."
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tvsjr is correct, this series of radios are not designed be peaked for operation an a particular frequency.

The VHF RF board front end has a 3dB bandwidth of 40 MHz and a 1 dB bandwidth of 35 MHz centered at 160 MHz. That means the performance of the receiver should be equivalent across the entive VHF band all the way to the bottom of the 2 meter band.

The UHF RF board is designed to cover from 449 to 470 MHz. It's front end is adjustable - however the service manual does not provide a procedure. The factory no doubt used a special test fixture and swept alignment equipment such as a network analyzer.

A careful alignment in the field should be able to shift the tuning of the UHF RF board to improve performance of the receiver in the 440 to 449 MHz range.

Look for a Maxtrac service manual [6880102W84]

Huh, guess I was mistaken. I thought that all radios were "tunable" to one degree or another.

Instead of focusing on the radio, shouldn't he be more focused on the antenna and duplexer system then?

601 wrote:Huh, guess I was mistaken. I thought that all radios were "tunable" to one degree or another.

Instead of focusing on the radio, shouldn't he be more focused on the antenna and duplexer system then?

Nope. As manufacturing processes get better, things are less and less tweakable. Look at the Spectra, which is almost 20 years old now... laser-cut VCO, fixed bandpass filters, etc.

Now, to come full-circle, as the RF front end gets done more and more in software rather than in hardware (DSP vs. discrete components), a radio could be much more tweakable. Just how much "tweak" Moto allows (without doing bad-nasty things like reverse engineering the firmware) is up in the air.

Probably the most recent Moto radio that had a tunable front end was the Syntor X9000.

Yes, you're quite correct... he should be focusing on the antenna and any RF conditioning in place. A good start would be to route the TXer to a dummy load, plug a signal generator in as far "out" as possible (generally where the antenna feedline connects to the duplexer or passes through into the building) and see what the sensitivity is like. Then, go from there.

Repeaters, like anything, are just a giant puzzle. Break it down, look at each piece, figure out how they interact, and solve the problem.

Thanks to all for the info. I spent most of today installing a Celwave super station master antenna and wow!! I hear and transmit! This is my first time experience with putting a repeater together. Tom

It is possible to get some small improvement for the receiver by bypassing the antenna switch on the PA board. Even tho the antenna switch circuit is a good design, there is some small loss and the posibility of the antenna diodes causing intermod.