Subject: Re: Commercial xceivers (was Re: Ramsey kits)

From: [email-masked] (Gary Coffman)
Date: 31 Jan 92 19:42:32 GMT

In article <[email-masked]> [email-masked] (Alan Bloom) writes:
>In rec.radio.amateur.misc, [email-masked] writes:
>
>>Last fall I decided to try my hand at the 2M transceiver. 
>>....  Everything went well until it came time
>>to see if the thing would receive.  I hauled out my HT and transmitted from
>>about 50 feet away and it worked!.  I then hung a J-pole onto the antenna jack
>>and tuned it to a local repeater.  Nothing!  It didn't even begin to receive.
>>I went back through all the steps and it was all correct.  The only thing I
>>couldn't be certain about were the alignment steps.  You need a freq counter.
>>The instructions warn you of that but believe them you _do_ need a freq
>>counter.
>
>Either the receiver is off frequency, or the front end or IF (intermediate-
>frequency amplifiers) are misaligned.  If there is a frequency discriminator
>output (test point) available, then just transmit on the HT and adjust the 
>crystal oscillator in the Ramsey synthesizer for zero volts on the test point.
>If said test point is not available, then have someone talk into your HT
>("Testing, 1, 2, 3...") while you listen on the kit, and adjust the
>oscillator for lowest audio distortion.
>
>To adjust the front end and IF tuning, you need a weak signal. Maybe  
>move the HT to another room or transmit into a dummy load.  Adjust each
>stage for lowest noise (receiver unsquelched).  As sensitivity improves,
>you will have to reduce the incoming signal to get the noise back.

Let me give you a few tips on aligning the Ramsey. Step one, ignore the
procedure in the book. Step two, inject a 10.7 Mhz signal into the IF
at L28 and adjust L24, L32, and L28 for best quieting. You'll need to
reduce injection several times as you alternate back and forth among
these coils. Now inject a 146.52 Mhz signal into the antenna input, or
use whatever frequency you have set into the diode matrix. Now stretch
L15, L26, and L27 for best quieting. Don't be surprised if you need to
stretch the coils to twice their supplied length. You should be down
to about .2 to .4 microvolts at this point. Now go back and repeak 
everything again with a .2 microvolt signal at the antenna. You should
get at least 12 db quieting. 

The preceeding procedure assumes that you have already used a frequency
counter to set the oscillators on frequency. If they don't come up within
range, you'll need to add padder capacitors. Depending on whether you are
high or low, you'll add 10 pf across the varactor or the crystal. Do this
on the back side of the board with minimum leads. If 10 pf won't bring 
them in range, call Ramsey and demand new crystals. They *will* give you
new crystals that will work.

Now on to the fun job of aligning the transmitter. First make sure that
you installed the chip capacitor *exactly* where Ramsey says to put it.
THIS IS CRITICAL. Now carefully monitor current and place the unit in
transmit. If the current fluctuates wildly, you've got a parasitic 
oscillation. Quickly adjust C47 and C52 to stop this. These capacitors
should have been preset to the center of their range. Now monitoring
output on a sensitive power meter, adjust C47 and C52 for maximum output.
If the adjustment winds up at the end of it's range, compress or expand
L14 or L17 until it comes into the center of it's range. You may have to
actually remove or add a turn to these coils to get it right. Your power 
will likely be around 2 to 3 watts at this point. Now compress or expand
L16 for maximum power. Again you may find that you have to subtract or
add a turn to this coil. Go back and repeak C47 and C52. You should now
have 5.5 to 6 watts out.

If you have access to a spectrum analyser, use it during transmitter
tuneup. This transmitter can be quite dirty at certain tuning settings.
Adjust for cleanest output even if that drops your power out by half a
watt or so.

Gary KE4ZV