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Re: Pre-amps



Bruce,
 I'm glad to have come upon this post as I was going to try and go the 
Ramsey kit route for a two meter preamp as well. I was going to use the 
RF switch and mount the whole thing in a weatherproof enclosure at the 
mast. Guess I'll have to rethink that.
 I love my ARR 70cm mast mount preamp but unfortunately  I can't afford 
the same on the two meter side right now so I'll have to come up with 
another solution.
 On a side note related to preamps, my TS-2000 doesn't have 13.8 VDC at 
the coax jack for preamp power so I use a bias tee. Should this be 
powered by a separate supply from the rig or does it matter? I'm using 
my  DC supply I use for my rig and have wondered if this was acceptable.
73,
Michael, W4HIJ

Bruce Robertson wrote:
> I've had some recent experience with 2m preamps that I thought I should add
> to this thread. These are not reviews, just another straw in the wind.
>
> Thinking that the NF of a 2m preamp is not as critical and being a
> confident and experienced homebrewer, I decided to do the Ramsey kit with
> the RF switch. I had two difficulties. The first was that the RF switch is
> designed for FM use and, out of the box, chatters on SSB and CW
> transmission. With the prompt help of the people at Ramsey, I altered the
> delay circuit, but it never became satisfactory. Secondly, and only
> speaking qualitatively, I didn't find the noise floor improved as a result
> of this unit. I tried tuning its tuned circuit, but I never got it right. 
>
> I then got a 2m preamp built into a second-hand 2m amp. The same problem as
> before: I expected the beacon of VO-52 to 'pop up' a bit from the noise
> when this was engaged. It just seemed that everything got louder. 
>
> More recently, I bought a proper mast-mounted low noise preamp built by
> ARR. This was a second-hand unit. It did the trick, lowering the noise
> floor in a manner similar to the 70cm unit I have.
>
> (The reader who has got this far might say, aha, but the mast-mounted unit
> will inevitably be better than the in-shack model due to the line loss and
> increased noise it causes. I don't believe this is the issue. I'm running
> only 40' of 1/4" heliax to the 2m unit, and my 70cm preamp to which I'm
> comparing is in-shack with a run that has a similar loss in its band.) 
>
> Reluctanly, then, I recommend a high-performance unit at 2m as well as
> 70cm. I am quite pleased with ARR equipment. I would be interested if
> others have had better luck with Ramsey RF switches, in part because I have
> a second one in the treasure chest waiting for another project.
>
> 73, Bruce
> VE9QRP
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