RE: [drakelist] Fw: TR7 Mike Gain

[Jim DiMauro]

Bill:

 

I assume from your post that low mic gain has always been a problem, since you said that you were surprised that the output of the mic did not improve when you switched mics.  Assuming that you have an acceptable impedance match, before you tear into the rig to do any mods or troubleshooting, don't overlook something as basic as alignment.  If your radio hasn't been aligned, it's possible that the transmitter ALC alignment needs touching up.  If you have a service manual, do the TX alignment.  Stay away from the 10 V regulator alignment, just go right to the TX alignment section and do all of the steps to the end.  You'll note there's a procedure for the ALC where you have to use a non-inductive dummy load.  They're not kidding: if you don't use a high quality dummy load the procedure won't work.  I tried with a Cantenna and it didn't work; I had to use a Bird load.  When the alignment is off, you'll get low power output, and the ALC light might come on only at a high mic gain setting, if at all.  The aligmnent procedure is simple and straightforward; just do it carefully and you'll have no trouble.

 

73,

Jim

WA2MER

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Eric Webner
Sent: Monday, January 03, 2005 7:56 AM
To: drakelist@www.zerobeat.net
Subject: Re: [drakelist] Fw: TR7 Mike Gain

Hi Bill,

 

I had a similar problem with my Kenwood TS-520 years ago when I replaced the mic element in my D-104 mike with a Heil. I tried several transformers to get the low impedance element up to the 50 k-ohm input the radio was looking for.

 

The final solution was to wire it direct without any transformer. I don't know if this will "increase" your audio so you don't have to run the gain as high, but it works great, and the audio is awesome!

73,

 

Eric KA8FAN

Bill Carpenter <[EMAIL PROTECTED]> wrote:

 

----- Original Message -----

From: Bill Carpenter

To: [EMAIL PROTECTED]

Sent: Sunday, January 02, 2005 8:52 PM

Subject: TR7 Mike Gain

I love my TR7 SN 7398 and use it quite a bit.  I replaced the muddy sounding cartridge in the 7077 mike with a Heil HC-5 element and reports on audio quality are much better now.  I was surprised that the output of the mike did not improve.  I still need to run the mike gain at about 3 oclock to light the ALC led and get full output on SSB.  Since the HC-5 is low impedance I wired it through the transformer in the 7077 so it would match the stock high impedance input of the TR7.  Is it possible to wire the mike a different way to increase output?  I have heard that later TR7 models have a second low impendence mike input and maybe that would solve my mike gain problem?

 

Thanks and 73,

 

Bill NZ0T

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