Re: [Repeater-Builder] UHF Preamplifier

[Kevin Custer]

Hi Dan,

I have used several of them in the past.  While they provide lots of 
preselection, they aren't great where NF is concerned.  I believe a 
simple 2 section BP Cavity and GaAs device to follow would easily beat 
the GLB in performance; both in preselection and NF.

Kevin

Dan Hancock wrote:

> Have you guys tried the Simrex (formerly GLB) helical resonator 
> pre-amp? It's great for repeater applications. Very selective and 
> moderate gain. If you're using Bp-Br type cans you don't need any 
> further filtering.
> http://www.simrex.com/site/products/preselector/Preselector1.pdf
>  
> http://www.simrex.com/site/products/preselector/preselector_diagram.pdf
>  
> I haven't bought one in quite a few years, but the last one I got was 
> in the $150 range.
>  
> Dan N8DJP





 
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Re: [Repeater-Builder] UHF Preamplifier

[Dan Hancock]

Have you guys tried the Simrex (formerly GLB) helical resonator pre-amp? It's great for repeater applications. Very selective and moderate gain. If you're using Bp-Br type cans you don't need any further filtering.  http://www.simrex.com/site/products/preselector/Preselector1.pdf     http://www.simrex.com/site/products/preselector/preselector_diagram.pdf     I haven't bought one in quite a few years, but the last one I got was in the $150 range.     Dan N8DJP         Date: Sun, 18 Dec 2005 08:26:10 -0800   From: [EMAIL PROTECTED]Subject: Re: UHF PreamplifierAt 12/17/2005 10:15, you wrote:>I've got the same setup. I also have a 4-section>Celwave bandpass filter between the duplexer and>preamp. I found that the 17dB gain was way too much>for the receiver, and the noise level increased>dramatically, to the point that I had to tighten the>squelch settings. The sig strength metering went from>10 to 14uA with no signal.Why is that such a bad thing?  If you add a preamp to a RX & your measured noise power doesn't increase, it means that the largest source of noise in your system is still your RX & that there's still room for improvement.Unless you're really worried about dynamic range, the ideal setup would be one in which the total noise power added by the addition of the preamp equals the noise present at the front end of the RX. 
 This should provide the best balance of system noise figure & dynamic range.  If a 10 to 14 uA change represents 3 dB, then you'd be all set at that point.I don't know what's up with your carrier squelch.  A well-designed squelch circuit shouldn't care how much noise power is present at the front end.  Perhaps there's another problem with the RX: low gain in an IF stage, limiter problem, etc. that's causing the discriminator output to change with input noise power.Bob NO6B__Do You Yahoo!?Tired of spam?  Yahoo! Mail has the best spam protection around http://mail.yahoo.com 













  




  
  
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Re: [Repeater-Builder] UHF Preamplifier

[Kevin Custer]

  
Think about this for a minute, if the noise level increased, the squelch
circuit would have seen MORE noise and rammed the squelch closed.
What actually happened is, adding a better device in front of the
receiver lowered the receivers total noise figure, decreasing the noise
in the squelch circuit, requiring the squelch pot to be set tighter.
Very common effect.

  
  
Common?  Must be another explanation, as you're talking apples & oranges 
here w.r.t. noise.  Remember this is FM, so more noise power at the front 
end doesn't mean more noise at the discriminator unless the limiter isn't 
being driven into limiting, which is probably what's happening.  But adding 
a preamp can only add total noise power, never subtract.

Bob NO6B


If what you are saying is correct, adding the preamplifier should have
placed a receiver lacking in overall gain into full (or at least more)
limiting.  If so, this would have raised the noise level to the
discriminator, thus tightening the squelch.  He commented that he
needed to set the squelch pot tighter, which means there was less noise
present after the installation of the preamp.  Maybe I didn't explain
it well, but I have seen this effect before, even on the bench where
extraneous signals quieting the receiver can be ruled out.

Kevin














  




  
  
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RE: [Repeater-Builder] UHF Preamplifier

[Mike Mullarkey]

That all depends on witch pre-amp you buy & what spec you need for your site
noise. I also swear buy his product. 

Oregon Repeater Linking Group
Mike Mullarkey
6539 E Street
Springfield, OR 97478
www.orlg.org
 
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of
[EMAIL PROTECTED]
Sent: Sunday, December 18, 2005 8:36 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] UHF Preamplifier

At 12/17/2005 10:21, you wrote:
>At 10:15 AM 12/17/2005 -0800, you wrote:
>
> >I found that the 17dB gain was way too much for the receiver
>
><---That's one reason I swear by Chip's stuff for over 15 year.
>
>He places stability and noise figure over gain. The result are preamps with
>extremely low noise figure, unconditional stability and reasonable gain
>(typically around 12 dB).
>
>Ken

I thought they were around 16-17 dB.  Chip claims 17 dB < 500 MHz; I once 
measured 16.

Bob NO6B






 
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Re: [Repeater-Builder] UHF Preamplifier

[no6b]

At 12/17/2005 10:21, you wrote:
>At 10:15 AM 12/17/2005 -0800, you wrote:
>
> >I found that the 17dB gain was way too much for the receiver
>
><---That's one reason I swear by Chip's stuff for over 15 year.
>
>He places stability and noise figure over gain. The result are preamps with
>extremely low noise figure, unconditional stability and reasonable gain
>(typically around 12 dB).
>
>Ken

I thought they were around 16-17 dB.  Chip claims 17 dB < 500 MHz; I once 
measured 16.

Bob NO6B






 
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Re: [Repeater-Builder] UHF Preamplifier

[no6b]

At 12/17/2005 11:07, you wrote:
>Bob M. wrote:
>
> >I found that the 17dB gain was way too much for the receiver, and the 
> noise level increased dramatically, to the point that I had to tighten 
> the squelch settings.
> >
>
>Think about this for a minute, if the noise level increased, the squelch
>circuit would have seen MORE noise and rammed the squelch closed.
>What actually happened is, adding a better device in front of the
>receiver lowered the receivers total noise figure, decreasing the noise
>in the squelch circuit, requiring the squelch pot to be set tighter.
>Very common effect.

Common?  Must be another explanation, as you're talking apples & oranges 
here w.r.t. noise.  Remember this is FM, so more noise power at the front 
end doesn't mean more noise at the discriminator unless the limiter isn't 
being driven into limiting, which is probably what's happening.  But adding 
a preamp can only add total noise power, never subtract.

Bob NO6B






 
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Re: [Repeater-Builder] UHF Preamplifier

[no6b]

At 12/17/2005 10:15, you wrote:
>I've got the same setup. I also have a 4-section
>Celwave bandpass filter between the duplexer and
>preamp. I found that the 17dB gain was way too much
>for the receiver, and the noise level increased
>dramatically, to the point that I had to tighten the
>squelch settings. The sig strength metering went from
>10 to 14uA with no signal.

Why is that such a bad thing?  If you add a preamp to a RX & your measured 
noise power doesn't increase, it means that the largest source of noise in 
your system is still your RX & that there's still room for improvement.

Unless you're really worried about dynamic range, the ideal setup would be 
one in which the total noise power added by the addition of the preamp 
equals the noise present at the front end of the RX.  This should provide 
the best balance of system noise figure & dynamic range.  If a 10 to 14 uA 
change represents 3 dB, then you'd be all set at that point.

I don't know what's up with your carrier squelch.  A well-designed squelch 
circuit shouldn't care how much noise power is present at the front 
end.  Perhaps there's another problem with the RX: low gain in an IF stage, 
limiter problem, etc. that's causing the discriminator output to change 
with input noise power.

Bob NO6B






 
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RE: [Repeater-Builder] UHF Preamplifier

[Jeff DePolo WN3A]

Like others have said, Lunar doesn't exist any more.  Angle Linear is the
current company, and Chip Angle makes great products.  However, if your ARR
is working, you are likely not to experience any measurable improvement in
performance by switching to something else (assuming the ARR you have is a
GaAsFET).  Personally I like Angle Linear's preamps a) because they work
well, and b) I've never had one fail out of probably 30 or 40 in service on
various bands, both ham and and otherwise.  YMMV.  And as others have
mentioned, proper filtering before the preamp is almost always necessary
(pass/reject duplexers often aren't enough).

--- Jeff



> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of mdnosliw
> Sent: Saturday, December 17, 2005 11:18 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] UHF Preamplifier
> 
> 
> I am currently running a AR2 preamp on my MSF5000 repeator with a 
> cellwave 526 duplexor. I was thinking if uogrsding to Lunar preamp, 
> but can find no reference to them on the internet. If anyone has any 
> contact information it would be appreciated.
> 
> Thanks
> Mark
> KB1IOZ
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





 
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Re: [Repeater-Builder] UHF Preamplifier

[Kevin Custer]

Bob M. wrote:

>I found that the 17dB gain was way too much for the receiver, and the noise 
>level increased dramatically, to the point that I had to tighten the squelch 
>settings.
>

Think about this for a minute, if the noise level increased, the squelch 
circuit would have seen MORE noise and rammed the squelch closed.
What actually happened is, adding a better device in front of the 
receiver lowered the receivers total noise figure, decreasing the noise 
in the squelch circuit, requiring the squelch pot to be set tighter.  
Very common effect.

Kevin




 
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Re: [Repeater-Builder] UHF Preamplifier

[Ken Arck]

At 10:15 AM 12/17/2005 -0800, you wrote:

>I found that the 17dB gain was way too much for the receiver

<---That's one reason I swear by Chip's stuff for over 15 year. 

He places stability and noise figure over gain. The result are preamps with
extremely low noise figure, unconditional stability and reasonable gain
(typically around 12 dB).

Ken


--
President and CTO - Arcom Communications
Makers of state-of-the-art repeater controllers and accessories.
http://www.ah6le.net/arcom/index.html
We offer complete Kenwood TKR repeater packages!
We are now an authorized Telewave Dealer!
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Re: [Repeater-Builder] UHF Preamplifier

[Bob M.]

I've got the same setup. I also have a 4-section
Celwave bandpass filter between the duplexer and
preamp. I found that the 17dB gain was way too much
for the receiver, and the noise level increased
dramatically, to the point that I had to tighten the
squelch settings. The sig strength metering went from
10 to 14uA with no signal. I ended up putting 7dB of
attenuation between the preamp and the receiver, but
still had too much gain. I later increased to a 10dB
attenuator. The receiver metering is resting at about
10.5uA, the squelch got reset to what it was with
nothing connected to the receiver at all, and there's
just enough gain to offset the losses from the coax,
duplexer, and filter, and still leave some for the
received signals.

If you aren't padding the preamp output down, you
should seriously consider doing so. The preamps are
made with all that gain so you can feed a lossy
multicoupler with them; when feeding one receiver, you
don't need or want all that gain.

Bob M.
==
--- mdnosliw <[EMAIL PROTECTED]> wrote:

> I am currently running a AR2 preamp on my MSF5000
> repeator with a 
> cellwave 526 duplexor. I was thinking if uogrsding
> to Lunar preamp, 
> but can find no reference to them on the internet.
> If anyone has any 
> contact information it would be appreciated.
> 
> Thanks
> Mark
> KB1IOZ

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Re: [Repeater-Builder] UHF Preamplifier

[Kevin Custer]

mdnosliw wrote:

>I am currently running a AR2 preamp on my MSF5000 repeator with a 
>cellwave 526 duplexor. I was thinking if uogrsding to Lunar preamp, 
>but can find no reference to them on the internet. If anyone has any 
>contact information it would be appreciated.
>

I haven't heard anything about Lunar in years, but if you want the best 
in preamps, try DEMI or Angle:


Kevin




 
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