Raj,
I have not measured the gain of the ATF stage by itself. That is
difficult to do because the measurement probe can induce and pick up
stray coupling at VHF/UHF frequencies.
I normally judged the overall performance of the XVseries transverters
by injecting a -140 dBm signal (controlled so there is little leakage)
with a connected receiver. I expected the receiver response of that
combination to show a 20 dB or greater audio signal above the receiver
noise floor.
In other words, I used a 'system approach'.
If the overall response was not acceptable, in all cases, replacing the
PHEMT corrected it.
73,
Don W3FPR
On 5/12/2019 2:29 PM, Rajiv Dewan wrote:
Thanks Don for your prompt reply.
I built it a few years ago and I think it worked then. I just got
back into UHF and thought to check it out. So, I am not sure if it
worked before.
I have peaked the RX cap and LNA bias.
I measured the gain across the ATF to be 10.5dB. Does that indicate
that the PHEMT needs to be replaced?
Raj, N2RD
------ Original Message ------
From: "Don Wilhelm" <[email protected]>
To: "Rajiv Dewan" <[email protected]>; [email protected]
Sent: 5/12/2019 2:03:48 PM
Subject: Re: [Elecraft] XV432 deaf
Raj,
Has this XV432 worked before and recently developed weak receive? If
so, try peaking the RX input capacitor, and if that does not correct
it, replace the PHEMT (ATF34143).
If you recently acquired it, check the configuration jumpers for the
28 MHz IF - do you have a single coax and it is configured for
separate TX and RX IF (or vice-versa)?
73,
Don W3FPR
On 5/12/2019 1:44 PM, Rajiv Dewan wrote:
Dear all,
I have a XV432 that seems deaf compared to my ICOM IC-7000. When
I tune to a local beacon on 432.300 MHz, I can copy it clearly on
the IC but nothing is heard on the XV432/K3 with KXV3B. I checked
transverter set up by feeding it a signal from a signal gen. It has
a conversion gain of about 16 to 17dB. The specs say 20dB. This
does seem to be too bad.
I checked the front end RF circuit out by feeding in a -80dBm
signal from HP8657B signal generator set to 432.300MHz. The
ATF34143 seems to have a net gain of 11dB. The next MMIC MAV11 seems
to have a gain of 10.5dB. Are these within spec?
If I can fix it without altering the circuit, that would be ideal.
Else, I am considering two mods:
Replace the MAV11 (10 to 12db gain in specs) with MAR8 (27dB gain)
with appropriate change in the bias resistor (120 1W to 270 ohms
1/4W)Insert a W6PQL LNA (uses PGA103+) between K10 and the ATF on
board.
Thoughts/ideas are very welcome,
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