Not yet..............I tried it with an outdoor antenna. Hooking it up to
the RF generator, though also poses no problems. I do notice one
problem.........when you peak the 455kHz I.F. transformers that feed the
1350 I.F. amps, the NF suffers. I notice that the circuit, as designed,
applies V+ to the high side of the primary instead of using the center tap.
This connection is also bypassed to ground. I think that if I feed V+ to the
center tap, that this problem should go away. I have used these devices in
the past, with no problems, but I did feed V+ through the center tap of the
primary.
I also noticed the the PIN diodes in the front end are being biased at 20mA.
PIN diodes should be biased at 75mA or so, for low "on" resistance. I am
going to reduce that 220 ohm bias resistor to around 47 ohms and see what
happens.
I haven't measured the Q of the front end coils, but I would surmise that it
isn't too high. I've got some magnetically shielded units with the same form
factor that have a Q of 50. This should improve the front end filter loss.
I did remove the 1k swamping resistor from the primary of the 1st 455kHz
I.F. transformer. Gain came up quite a bit, so the radio sounds more like a
651S-1 or a 75A-4.
I'll let you folks know how things turn out, once I finish with the radio.
It really is a cool radio.

Pete

"clvrmnky" wrote in message
...
On 25/02/2005 3:09 AM, Pete KE9OA wrote:
I just got finished building one of these things. It is not quite stock.
I used film caps in the audio chain and the synthesizer loop filter,
silver micas in the RF filters, a Murata CFR series filter in the I.F.
strip, matched hot carrier diodes in the 2nd mixer, and 1N5767 PIN diodes
instead of the stock attenuator diodes.
At 15MHz, MDS is .06uV. No overloading was noted on any band, including
49 Meters. System gain is quite high.
MW performance isn't too hot, but it could be the input filter. I might
use a design of my own and see how it works out.
I had seen this unit in the past, but I didn't want to pay 200 dollars
for a kit..............this radio kit was part of a trade I made a couple
of weeks ago.
Knowing what I know now about this radio, I would say it is worth the kit

Nice. Are you getting the birdies below 7MHz that some people think are
caused by IF from the LED display?

The AGC is reported to be a bit harsh on AM. Have you noticed this, or is
it as bad as the report of eham.com suggests? I wonder if your tolerance
tweaks in the IF stage helped in this regard.

What kind of antenna do you have hooked up to this? I understand Ten-Tec
advises using a long shielded hookup to the antenna. I might be tempted
to replace the phono jack with BNC or coax to make this easier. Though, I
suppose shielded cables meant for audio applications are a dime-a-dozen.