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XV432 deaf

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Rajiv Dewan

XV432 deaf

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,

Raj

--

Raj Dewan, N2RD
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Don Wilhelm

Re: 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,
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Rajiv Dewan

Re: XV432 deaf

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,
>>

Don Wilhelm

Re: XV432 deaf

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" <[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,
>>>
>
>