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Re: Why V/S in stead of U/S



Margaret Leber said:
> Mike Murphree wrote:
>
>> The Drake required no IF mods if you converted to the 430 MHz IF and
>>  the crystal is commonly available at DigiKey, etc.
>
> "The Drake required no IF mods...if you modded it"? :-) The 2800 ran
> pretty good (for a Drake) out of the box on an 847.

IIRC, the lower limit on the Drake's IF was around 300 MHz.  If you
changed the crystal alone for a VHF IF, then you lost a lot of gain. 
There was no such problem with the UHF IF, change the crystal and you're
done.


> Look, people, I've explained why I think switching to V/S is a major
> headache if you already equipped for U/S on a shoestring. Obviously a
> lot of you have an equipment budget where that's not an issue for you,
> so you can quit explaining to poor old Maggie why she's wrong.

You said that you had two Drakes, modify one of them. The Digi-Key part
number for the crystal is: 300-6016-ND and it only costs 70 cents, hardly
outside of anyone's budget.

As to why this personal inconvenience has been levied upon you, Andrew
explained it a couple of days ago:

Date: Mon, 23 May 2005 13:49:52 -0400 (GMT-04:00)
From: Andrew Glasbrenner <glasbrenner@mindspring.com>
Subject: Re: [amsat-bb] Why V/S  in stead of U/S

>Maybe I have missed a discussion somewhere, but I do not understand why
>AO-51 is using V/S instead of U/S.

To operate in a U/S mode, AO-51 would have to employ it's SQRX tunable
receiver. The command station has stated in the past that he considers it
unnecessarily risky to operate the SQRX on U band receive with 2 high
powered UHF transmit antennas 9 inches away. If one of the UHF
transmitters was somehow powered up while the SQRX was on U band, we could
loose the SQRX.

Additionally, The V band uplink requires no doppler correction for the
entire pass. A U band uplink would require about +/- 10 khz of tuning.
Combined with the +/- 60 khz of S band doppler correction it would almost
make computer tuning a requirement for many operators.

On a personal note, I don't know any sat ops with S band that do not have
a second 2m FM transmitter. Just about anything will work on the uplink,
demonstrated by the dozens of QSOs made on just 5 watts and a rubber duck
for uplinking during the last 2 V/S sessions. Visitors to the Dayton
Hamvention demonstrations can attest to this.

I hope that helps answer your question.

73, Drew KO4MA


--------

Mike W4LNA
----
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