70-340A tuning

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mercyh
Posts: 2
Joined: Thu Feb 21, 2008 12:42 pm

70-340A tuning

Post by mercyh » Thu Feb 21, 2008 12:49 pm

Hi,
I have a pair of Midland 70-340A radios that have the RFGUYS programmable 80 channel eeprom modules. These units have been tuned down into the 2 meter ham band. (142-148 freq) I need to get them back up into VHF Business band (151-159 freq.) The programming is no problem. My question is about tuning and alignment.

Is there a way to do this without the Midland test set? Can it be done with just a multimeter?

Royce

mercyh
Posts: 2
Joined: Thu Feb 21, 2008 12:42 pm

Re: 70-340A tuning

Post by mercyh » Wed Mar 05, 2008 2:18 pm

Hi,

I can get the tx side to tune fine without any more equipment. I am stumped on the rx side. The shop manual says to monitor certain pins and adjust for maximum indication with an on frequency tone generator attached. I thought I could replicate this by transmitting from another unit on that frequency and adjusting to highest possible voltage on the referenced pins. This does not work. What indicator am I looking for on the rx side?

Royce

k2hz
Posts: 150
Joined: Sun Jan 30, 2005 1:02 pm
Location: Rochester, NY

Re: 70-340A tuning

Post by k2hz » Wed Mar 05, 2008 7:52 pm

I do not have details on that particular unit but you can never align a receiver with a strong signal from a nearby transmitter. You must use a signal generator adjusted to produce a signal below the threshold of limiting (less than full quieting). As you progress with the alignment you must continually reduce the signal generator output.

Once the limiter is saturated, you will not see any change at the metering points as you attempt to tune.

You may be able to adjust the receiver oscillator and multipliers if test points are provided but the RF alignment must always be with a weak signal.

telemetryguy
Posts: 4
Joined: Mon Dec 05, 2011 6:40 pm

Re: 70-340A tuning

Post by telemetryguy » Tue Jan 10, 2012 5:13 pm

I have one of the RFguys modules in my 29 mhz Syntech I. I lost the documentation for the module. I cannot get the computer's parallel port to communicate with the module. I set the port for EPP and set up everything like the README file on the program disk says, but no go. Do either of you have any ideas? I need to add a scan list. Thanks

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