Batboard

I am in the process of recrystalling an MSR2000. The receiver was fine with the origional channel element, but is deader than a door nail with the recrystalled element. The RX is going from 453.XXX to 462.XXX. Is there an easy way to tune the channel element before it goes into the radio per: http://www.repeater-builder.com/mitrek/ ... ments.html

I had this same problem with a mitrek years ago, is it just me or are these receivers really a bear to get going when changing frequency in them?

Thanks, Bill.

That much frequency change would probably require a complete realignment of the receiver. You need a meter or test set, and a good signal generator. There wouldn't be much to tune on the channel element itself except for the frequency, and it's not critical when you're doing the alignment.

Your biggest problem would likely be the multipliers and mixer tuning.

Bob M.

I have all the equipment, and manuals for the realignment. Even with setting everything to the presets the receiver is still DOA. There is an adjustment inside the channel element fo peak the output from the osc.

Bill.

My two bits worth:
I have done many of these.
Using an RF milivolt meter, or your spectrum analyzer determine if there is any output from the channel element.

Perhaps the crystal is defective, or there is a solder "splash" on the channel element. I found a piece of wire in a FACTORY element once causing intermittents.

There are two coils for setting the crystal on frequency. I calculate the injection frequency and use my monitor to set freq.

This has nothing to do with your problem, open the harmonic filter on the PA for inspectipon of the solder..I have seen many of these burn.

The channel elements are the same as MITREC.

Anybody ever try replacing the channel elements with a programmable synthesizer? I have several MSR's I'd like to be able to put out as field loaners if it were as easy as programming a synthesizer & retuning the repeater. If so, any recommendations on a manufacturer?

Todd

wavetar wrote:Anybody ever try replacing the channel elements with a programmable synthesizer? I have several MSR's I'd like to be able to put out as field loaners if it were as easy as programming a synthesizer & retuning the repeater. If so, any recommendations on a manufacturer?

Todd

Wow ... that is really asking for quite a bit.

In years past I have used the old VHF Engineering Synthesizer with such radios as the U43HHT1100E Motrac series and even designed small synthesizers for use in Low-band Motrac and Micor series radios (these were designed to mount in the radio, with channel control via the channel select lines to the radio).

The problems that arise include spectral purity (the VHF Engineering Synthsizer was 'dirty' close in) compatibility (size, output into the target radio multiplier chain and 'microphonics' (subject to vibration induced FM effects) of a small, FR4-board based after-market quality synthesizer.

And anytime you have a 'tuned' radio (honest to goodness hardware in the front end and multiplier chains) it takes reallignment if you exceed the natural 'spread' the radio is rated for. It was tough, for instance, to get a VHF Motrac to do the Two Meter Ham band without the RF PA final tube's plate current from soaring out of control on band edges!

Jim / WB5WPA