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RX Ant K3 Preamp vs External Preamp

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Rich-4

RX Ant K3 Preamp vs External Preamp

I am interested in finding out from the experts....................

Is it best to use the K3 internal pre-amp or add an external pre-amp to
the RX antenna system?

Thanks

Rich

K3RWN

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Bob McGraw - K4TAX

Re: RX Ant K3 Preamp vs External Preamp

The internal preamp in my K3S does an excellent job on 6 meters. If I
decided to use an external preamp, it would be located at the antenna
feed point with suitable switching and protection.

I suppose the question, what bands do you perceive you need a preamp?
And what is your no signal band noise on the bands of concern?

73

Bob, K4TAX

On 4/26/2020 6:32 PM, Rich wrote:

> I am interested in finding out from the experts....................
>
> Is it best to use the K3 internal pre-amp or add an external pre-amp
> to the RX antenna system?
>
> Thanks
>
> Rich
>
> K3RWN
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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donovanf

Re: RX Ant K3 Preamp vs External Preamp

A good rule of thumb is that if receiver background noise level drops at
least one S-unit when the antenna is removed, then receiver sensitivity
is externally noise limited. This may be hard to achieve on 6 meters
unless all losses from the antenna feed point to the receiver input are less
than 2 dB and impossible to achieve on 2 meters and above unless total
losses are less than one dB.

This rule-of-thumb is very valuable on the lower bands because it helps
the operator select the proper receiver attenuator and RF preamplifier
settings for optimum dynamic range while retaining full system sensitivity.
You'd be surprised how few DXers and contesters understand this simple
principle, and fewer still actually do it when they sit in front of their
receiver.

73
Frank
W3LPL

----- Original Message -----

From: "Bob McGraw K4TAX" <[hidden email]>
To: [hidden email]
Sent: Monday, April 27, 2020 12:12:56 AM
Subject: Re: [Elecraft] RX Ant K3 Preamp vs External Preamp

The internal preamp in my K3S does an excellent job on 6 meters. If I
decided to use an external preamp, it would be located at the antenna
feed point with suitable switching and protection.

I suppose the question, what bands do you perceive you need a preamp?
And what is your no signal band noise on the bands of concern?

73

Bob, K4TAX

On 4/26/2020 6:32 PM, Rich wrote:

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Rich-4

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by Bob McGraw - K4TAX

I was talking about RX antennas, like Beverages and such, so mainly 40m
and 80m. I am happy with the K3 pre-amp I was just curious to what
others use

Thanks

Rich

On 4/26/2020 20:12 PM, Bob McGraw K4TAX wrote:

> The internal preamp in my K3S does an excellent job on 6 meters. If
> I decided to use an external preamp, it would be located at the
> antenna feed point with suitable switching and protection.
>
> I suppose the question, what bands do you perceive you need a preamp?
> And what is your no signal band noise on the bands of concern?
>
> 73
>
> Bob, K4TAX
>
>
> On 4/26/2020 6:32 PM, Rich wrote:
>> I am interested in finding out from the experts....................
>>
>> Is it best to use the K3 internal pre-amp or add an external pre-amp
>> to the RX antenna system?
>>
>> Thanks
>>
>> Rich
>>
>> K3RWN
>>
>>
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

donovanf

Re: RX Ant K3 Preamp vs External Preamp

Hi Rich,

There's a very broad variety of receive-only preamps on the market.

I use the many Advanced Receiver Research P1-30/20VD preamps
in my station and I've always been very pleased with their performance
from 160 through 40 meters. Because they're broadband preamps, they
should have a simple receiving bandpass filter ahead of the preamp.

www.advancedreceiver.com/page46.html

If you're a technically inclined amateur there's an excellent overview here:

ac0c.com/main/page_homebrew_preamps.html

73
Frank
W3LPL

----- Original Message -----

From: "Rich" <[hidden email]>
To: [hidden email]
Sent: Monday, April 27, 2020 3:26:20 AM
Subject: Re: [Elecraft] RX Ant K3 Preamp vs External Preamp

I was talking about RX antennas, like Beverages and such, so mainly 40m
and 80m. I am happy with the K3 pre-amp I was just curious to what
others use

Thanks

Rich

On 4/26/2020 20:12 PM, Bob McGraw K4TAX wrote:

alorona

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by donovanf

Precisely the intended application for a visual aid to show where the sensitivity of the receiver sits relative to the band noise. W3LPL is absolutely correct in asserting that relatively few know how to optimize their settings for a given band condition.

Just sayin'.

Al W6LX

><[hidden email]> wrote:

>This rule-of-thumb is very valuable on the lower bands because it helps
>the operator select the proper receiver attenuator and RF preamplifier
>settings for optimum dynamic range while retaining full system sensitivity.
>You'd be surprised how few DXers and contesters understand this simple
>principle, and fewer still actually do it when they sit in front of their
>receiver.

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Jim Brown-10

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by Rich-4

On 4/26/2020 4:32 PM, Rich wrote:
> Is it best to use the K3 internal pre-amp or add an external pre-amp to
> the RX antenna system?

Unless you operate in a VERY quiet location, it's hard to beat the
preamp in the K3S (and that was offered as an accessory for the K3). The
preamp in the original K3 was not very good, and really needed the
accessory unit they offered for 12M and above.

I have a outboard GAsFet preamp designed for 6M that is slightly better
than the K3S preamp, and that I bought long before there was a K3. As it
turns out, it also works well down to 12M. I used it with my K3 at the
patch point. I've since replaced the transverter module in my K3s to
get that upgraded preamp.

Bob is certainly correct about the virtue of a preamp at the antenna,
but the 6M antenna on which I would use it is within 10 ft of two
antennas with which I run legal limit, and I have concerns that it would
survive up there. :) My compromise is 7/8-in hard line for those
antennas, which minimizes the loss, and thus the advantage of a
mast-mounted preamp.

73, Jim K9YC
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Jim Brown-10

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by Rich-4

On 4/26/2020 8:26 PM, Rich wrote:
> I was talking about RX antennas, like Beverages and such, so mainly 40m
> and 80m. I am happy with the K3 pre-amp I was just curious to what
> others use

As always, W3LPL's response is pretty much on the money for this. The
slightly longer short answer is that it depends on the antenna and the
noise where you use it. Some RX antennas have far higher output than
others. Beverages, for example, have fairly high output, so the preamp
built into most radios is plenty good enough, even in a quiet location.
Smaller antennas are more likely to need an outboard preamp. Some need a
preamp at the antenna. There's greater discussion of this in this piece
that I wrote for National Contest Journal a few years ago.
http://k9yc.com/RXChokesTransformers.pdf

73, Jim K9YC
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Edward R Cole

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by Rich-4

Assuming this question is for the K3, K3S, and K4, then the only
bands that preamp NF and preamp location matter is on 10m & 6m.

I run eme on 50, 144, and 1296 MHz; at 144 and above a so-called
masthead preamp (close to antenna) makes a difference in receiver
sensitivity (ability to hear the weak one's).

At 50-MHz I use an ARR P50VDG preamp at the base of my eme
tower. But its a very marginal improvement over using the PR6 on
back of my K3. For all non-eme operating I just use the PR6. I
believe the PR6 is not needed in the K3S and K4.

If your coax line loss is under 1-dB locating the preamp at the radio
works fine. Most 6m-eme stations have under 1-dB loss and place
their preamp at the radio.

PR6 helps my 2010 era K3 on 10m as well. I never use the internal
preamp with either the PR6 or ARR preamps, but sometimes use it on
20m or 17m. 30, 40, and 80m do not need any preamp as those bands
are sky noise limited (for most of us).

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
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Edward R Cole

Re: RX Ant K3 Preamp vs External Preamp

In reply to this post by Rich-4

Indeed!

Most eme'rs encounter this issue some point in their operation.

I started out on 144-MHz with only 100w on CW. Then began use of
digital in 2003. But it was not until I started running above 800w
in 2011 that I began to see preamp failure. I like my preamps to not
see RF over 0 dBm (1mw) so that implies the need for 61.8 dB
isolation if running 1500w. Initially I was using a coax relay with
only 45-dB isolation. So I upgraded to better relays (spec >
80-dB). But there are two other paths for RF to reach the
preamp: 1) thru the dc power leads (solved by using RG-58 for my
power leads), 2) poor shielding in coax jumper from relay to preamp
(solved by using double-shielded RG-142).

I also use a sequencer for controlling relay and amp transfer to
transmit (to avoid hot-switching the relay).

These are probably good arguments for using the internal preamp in a
K3S or PR6 at the K3. Internal TR switching protects them.

73, Ed

but the 6M antenna on which I would use it is within 10 ft of two
antennas with which I run legal limit, and I have concerns that it would
survive up there. :) My compromise is 7/8-in hard line for those
antennas, which minimizes the loss, and thus the advantage of a
mast-mounted preamp.

73, Jim K9YC

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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