Adjustment pots on a Maxtrac UHF HLE9310C rf bd.

[Satelite]

Hello:
On the Maxtrac RF bd HLE9310C .
The three blue adjustable pots .
R60 pot per the schematic adjusts the sqeulch .
R164 pot adjusts what ?????
R302 pot seems to adjust deviation level for the transmtter modulation ?????
Can someone confirm the pots and there intended use.
Thanx Satelite

[PETNRDX]

R60 is squelch.
R164 is the Reference oscillator deviation.
R302 is the VCO modulation.

[Satelite]

Hello:
Thanx a miliion.
That will most certainly help me out.
Satelite

[kcbooboo]

We're waiting for what should be the next obvious question: "What procedure do I follow to adjust R164 and R302?"

Bob M.

[Satelite]

Hello :

Not saying this is what the manual would say - if you can find it = i couldnt but :

R302 being the VCO modulation - The fcc already set the level by law per the radio .
So assuming your still legal to operate at 5 khz of audio - youd set the modulation at 5khz wide modulation per the service monitor.
Bear in mind that in 2013 that 5khz of modulation on most freqs will be reduced to 2.5 khz modulation.
This being due to the FCC implementing the 25 khz wide band and changing to 12.5 khz narrow band ruling going into effect 2013.

Edited to remove my previous posting of what i thought R164 pot did.
Done to prevent others from getting confused.
I was wrong earlier on R164 being the freq adjustment per the bd and now stand corected that its the PL / Subaudible tone adjustment pot.

Thanx satelite

[PETNRDX]

The VCO modulation is for voice type audio, either mic or even data, DTMF tones, etc.
The REF modulation is for sub-audible tones ( PL)
R164 won't affect the RF frequency there is a coil next to the 14.4 crystal that affects the frequency.
I have found that using the REF moduation pot for best PL waveform and partially to get the correct level works best for me.
And the VCO mod for mic deviation.
Once they are close, I use the RSS to get them exactly were I want.

[com501]

Keep in mind, that even though you turn the deviation down on that radio, it won't be compliant or type accepted after 1/1/2013 due too frequency stability.

[jackhackett]

R164 won't affect the RF frequency there is a coil next to the 14.4 crystal that affects the frequency.

You shouldn't use the coil to adjust the frequency, you should use the RSS. Adjusting the coil will affect the temperature compensation. Those tuning data numbers you have to put in when you do a board or crystal replacement are calculated for where the coil is set at the factory and tell the radio how to compensate for the temperature drift of the components, adjust the coil and your radio will go off freq. when it gets hot or cold.

[Satelite]

Hello:
Boy am i lucky.
I didnt turn any of the coils as from my experimenting i didnt see the need.
But its obvious i didnt have a complete understanding of the coils and R164.
Think ill go back and recheck my setting of R164 for the PL tone on the service monitor for decode / encode .
Thanx satelite

[PETNRDX]

This brings up a good topic.
What I have been doing is get the radio on and up to proper temperature.
Verify the tuning info has been entered properly.
Verify the RSS freq warp is centered.
Check the 14.4 against GPS disciplined freq counter ( or the service monitor ) if not on freq, then correct freq with crystal coil.
Then go thru the alignment.
Is there a better method?
I have not had a new board to deal with for YEARS.
So, have been using this method when repairing old radios primarily for the hambands.
And have had good results, no problems with temp drift.
Open to suggestions if there is a better way to do this.

[com501]

Yes, using the RSS alignment menus is the preferred method. However, unless you are willing to calibrate the radio in your environmental chamber, I don't think it matters too much. I usually do the software alignment and only touch the master osc. if the radio refused to get on frequency which happens sometimes with these old radios, due to component drift...

[Satelite]

Hello kcbooboo :
Well you brought up a darn good qestion above on the how do you do the adjustments properly.
Id really like to see the proper procedure for R164 and R302 adjustments .
Would you by chance have that info ?
Apreciate the input.
Thanx satelite

[kcbooboo]

There's nothing about any board alignments in the MaxTrac manuals. The GM300 hardware manual at least tells you how to adjust the reference oscillator frequency. The narrow-band mod for the GM300 tells you to adjust the two pots for 50% of the deviation that was present initially. The manual for the R100 station, which is based on a pre-MaxTrac radio, provides steps for adjusting the REF MOD, but since this radio doesn't use RSS for alignments, you have to adjust the pots.

I have my own ideas but nothing in writing. I merely wanted to open the flood gates and watch stuff float out.

Bob M.