Re: XV432 deaf
Posted by
Rajiv Dewan on
May 12, 2019; 6:29pm
URL: http://elecraft.85.s1.nabble.com/XV432-deaf-tp7651572p7651574.html
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" <
[hidden email]>
To: "Rajiv Dewan" <
[hidden email]>;
[hidden email]
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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