[TenTec] Corsair II Mixer Balance Adjustment

[K4MT]

Thanks Steve:
I only hear a tone at 21316 and not 21320. Why it is not in the correct spot if that is even it is unknown to me.
I discovered I could dip it out to almost nothing but the adjustment does not work as I would expect. There are two dips on the larger capacitor.  Logic would tell you one of them must be the correct dip. But when you use those dips the pot has no effect at all. I found the correct spot is close to the deeper of the two dips. You dip it and come back just out of the dip and find the spot where the pot starts to dip the tone. You then bounce between the pot and the two caps for the best dip.  After doing that I could barely hear the tone and RX sensitivity was still normal.
I will try injecting a 21320 as you suggest to make sure I have the balance adjusted at the right frequency.
Thanks,
Gary K4MT
--- On Thu, 12/27/12, Steve Hunt <steve at karinya.net> wrote:

From: Steve Hunt <steve at karinya.net>
Subject: Re: [TenTec] Corsair II Mixer Balance Adjustment
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Date: Thursday, December 27, 2012, 1:40 PM

I hear the 21,320 kHz "birdie" on both of my CorsairIIs at pretty high level.

The birdie tunes at 3 times the VFO rate; I believe it is the 9MHz product caused by:
3 x VFO - HFO = 3 x 5,330 - 6,990 = 9,000 MHz

The amplitude changes depending on whether I'm using my DDS VFO or my PTO - I guess they have different levels of third harmonic content.

You could try injecting a 9MHz signal directly on the LO input - connector 71 - and nulling that.

Hope that helps,
Steve G3TXQ





On 26/12/2012 18:35, K4MT wrote:
> I am finishing the work on my Corsair II and I decided to do the mixer balance adjustment.
> The manual says to null the tone at 21,320 but I have no tone there. I adjusted the alignment points for mixer balance thinking it might be already nulled but the null seemed to good to be true. Adjusting the null capacitor and pot produce no tone at all. I hear a tone at 21315 (yes, my dial is calibrated properly). I can null that tone but it kills the receive in that entire portion of 15 meters from around 21250 to 21400.  Surely that is not the correct one.
> Is there another way to do mixer balance adjustment or do I have a problem on that board? The radio seems to perform properly otherwise.
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