[Premium-Rx] Introduction, and a RF-590A question

Mon Aug 11 10:57:51 EDT 2014

Regarding the preamp location (pre or post feedline) I suspect that for most 
coax at the frequency range of this receiver it wouldn't make much difference.  
A chart I found shows that even cheap RG-58 loese 1.4 dB at 10 MHz per hundred 
feet.  Most installations use less feedline than that, and if you are needing a 
longer run most people who have a $16k premium receiver would spend a few bucks 
on better feedline and get that figure down to 0.5 dB per hundred feet.  At 
those losses you'll need good instrumentation to detect the difference between 
the location of the preamp.

I've use the preamp at antenna trick for VHF/UHF and it makes a difference, that 
was with a WJ receiver and there was about a 6 dB improvement which is an 
audible change.

As well, preamp design isn't a trivial problem.

Peter

On 8/10/2014 12:30 AM, Ahmet G. wrote:
> I would never use the A19 and agree with others.  Inserting Inductors, 
> capacitors and relays into the signal chain does
> take its toll, especially considering all these components are also aged and 
> maybe noisier than when they were first used.
> Maybe using a Roofing filter ( with a constant impedance diplexer ) instead of 
> the 16Khz first IF filter would be a better idea.
> RF591 still seems to be similar to A19 in that it has 60db attenuation +/-10% 
> of tuned frequency.
> Say at 10Mhz this is a 2 Mhz Bandwidth, quite large. What makes it sound 
> better is the preamplifier in it.
> However for receiver applications placing the preamplifier at the antenna 
> ahead of the feedline would actually
> lower the overall NF of the entire system even if RF590's NF is higher than 
> the preamplifier's.  I think it also lowers the Noise Floor
> as well.  It is actually a simpler setup (except it requires a bias T to feed 
> the preamplifier and a good filtered power source).
> Advanced Receiver's 30Mhz preamp NF is 2.5db with a 20dB gain.  Using this 
> preamplifier overall system NF will be lower than 4dB !...
> Also lowering the noise floor.
> With the preamplifier at the receiver end with a 10db NF, the overall NF will 
> be higher than 10dB for sure.
> Ahmet Gundes
> Interesting. It calls out a NF of 10 dB which isn't far from that of the
> receiver itself. There are some real low NF preamps out there now but things
> like AM broadcast swamp them so you need filtering before them, so if you're not
> careful up goes your NF again. Still, I would love to have one of those
> RF-591A's but haven't seen any around at anything near what I could afford.
>
> Peter
>
>
>
> On 8/7/2014 6:58 PM, Chuck Maurer wrote:
> > I agree with Peter. I have two RF-590A's and both came with the A19
> > preselector and I promptly disconnected both A19 modules and the 590A's came
> > alive. I also have a RF-591A pre/postselector which is a different story.
> > This baby really works. It is a separate housing and is connected to a
> > special interface board in the 590A. It has RF filtering that is
> > automatically controlled by the interface or its front panel. It also
> > contains several RF amplifiers. You can here a distinct improvement in signal
> > strength and selectivity but at a price......
> >
> > See RF-591A at
> > http://www.torontosurplus.com/harris-rf-591a-04-pre-postselector.html
> >
> > Inline image 1
> >
> > Chuck
> > W5API
> >
> >
> > On Thu, Aug 7, 2014 at 5:29 PM, Peter Gottlieb <hpnpilot at gmail.com
> > <mailto:hpnpilot at gmail.com>> wrote:
> >
> > I can go take photos of how mine is connected but first let me ask you why
> > you want it? The receiver is very selective without it, and it is
> > designed to make the receiver functional in an installation where there
> > are multiple high power transmitters running while it is receiving. You
> > lose a bunch of sensitivity by having it in line. I have a mod which uses
> > the NB button to bypass the preselector and I've found over the years that
> > I have not found a situation where I needed the preselector.
> >
> > Peter
> >
> >
> >
> >
> > On 8/7/2014 6:11 PM, Brian Gieryk wrote:
> >
> > Hello to the list from a new member.
> >
> > My name is Brian Gieryk (KE6IYC, 1994) and I currently reside in Apple
> > Valley, CA.
> >
> > I am a Television Transmitter Engineer by trade, but do a lot of other
> > things, as well.
> >
> > Currently, I drive an Icom IC-R9000, and a Harris RF-590A as my
> > primary receivers.
> >
> > Most of my interest lies in monitoring Fire comms, and anything odd I
> > can find from DC to Daylight, as they say.
> >
> > I am also very interested in an all band (HF, 2-30) vertical, that
> > works without a tuner...
> >
> > Now for my question,
> >
> > My 590A has a preselector (thanks to Mike Murphy) but I do not have
> > any of the cabling to connect it to the radio.
> >
> > Can someone provide details on just how it connects?
> >
> > I have a full factory original manual, but someone who has added the
> > preselector would be better to advise on what to do or not do.
> >
> > Thank you in advance,
> >
> > Brian
> > KE6IYC
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> > --
> > L.O.Chuck Maurer
> > President
> > Alternative INK
> >
>
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