New to list; My first question

[Larry, KB5HMU]

Hello fellow Hams,

I'm new to the list and was referred by many from the Yahoo K3 group. Thank you.

I have been wanting a new radio for a while now and the K3 is at the top of my list. My current radio, a 706 MkIIG, has performed well for the last 11 years but my interest in weak signal 6 and 2 meter operation leaves quite a lot to be desired. I'm not the sort that runs out and buys the newest or latest (I'm still driving my 1991 Accord EX) so I want a radio that will last me 20 years or more. This is what really led me to K3 as it can be updated anytime. I have been looking at the SDR radios but I'm really a "hands-on-the-knob" kind of operator. At field day I watched a ham at his gigantic Flex 5000C and 23" monitor. Very impressive at first sight but after watching for a while, I noticed that his entire operation was nothing more than continuous wrist motions with the mouse. Just don't think I can go there.

I hope to learn much more about the K3 as I bank away my extra dollars. It looks like I need to buy quite a few of the options to do the K3 the way I need (Ha-Ha: NEED) for my operations. Two meter board, ATU, DVR, a few filters and the Panadapter are a must for me.

Here's my first question to the group:
I enjoy 6 meters immensely and someone recommended that I buy the pre-amp. My understanding about the effectiveness of a VHF preamp is to amplify the highest signal, i.e. at the antenna, to give the lowest noise increase. The PR6 mounts at the radio. Wouldn't that be amplifying noise in a weak signal more than if it were mounted at the antenna?

Thanks,
Larry
KB5HMU
http://qrz.com/db/KB5HMU
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[Alan Bloom]

On Sun, 2011-07-03 at 11:02 -0700, Larry, KB5HMU wrote:

> Here's my first question to the group:
> I enjoy 6 meters immensely and someone recommended that I buy the
> pre-amp. My understanding about the effectiveness of a VHF preamp is
> to amplify the highest signal, i.e. at the antenna, to give the lowest
> noise increase. The PR6 mounts at the radio. Wouldn't that be
> amplifying noise in a weak signal more than if it were mounted at the
> antenna?

Yes, theoretically it is always better to put the preamp at the antenna
end of the feedline so that the noise figure is not degraded by the
feedline loss.  However, that is less of an issue on 6 meters than on
the higher VHF/UHF bands because:

(1) Coax cable loss is less at the lower frequency and

(2) Background noise is higher on 6 meters so that a super-low noise
figure is not as necessary.

It depends on what you're doing.  If you are into 6 meter moonbounce or
you have a long and/or lossy feedline then a remote preamp would be
worthwhile.

Alan N1AL


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[Fred Townsend]

Larry much has been written about defining the signal to noise ratio of a
receiver. You might want to search on this subject.

Hopefully I can simply things a bit. It is the designer's goal to get the
receiver noise lower than the ambient noise. Once that is done you are at
the mercy of the ambient noise. Likewise the design goal of a preamp is to
amplify the signal without increasing the noise figure. Sure the preamp
amplifies noise too. The key is the signal to noise ratio should not be
deteriorated by the preamp.

Now as to the location of the preamp. Yes ideally it is better at the
antenna. Many TV antennas have preamps at the antenna but TV systems are
receive only. If you are transceiving at antenna then whatever preamp you
use must tolerate your transmit power or somehow switch out the preamp on
transmit. Without going into detail preamps at the antenna are very
difficult to do if transmit signals are involved.

73

de Fred, AE6QL
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Larry, KB5HMU
Sent: Sunday, July 03, 2011 11:03 AM
To: [hidden email]
Subject: [Elecraft] New to list; My first question

Hello fellow Hams,

I'm new to the list and was referred by many from the Yahoo K3 group. Thank
you.

I have been wanting a new radio for a while now and the K3 is at the top of
my list. My current radio, a 706 MkIIG, has performed well for the last 11
years but my interest in weak signal 6 and 2 meter operation leaves quite a
lot to be desired. I'm not the sort that runs out and buys the newest or
latest (I'm still driving my 1991 Accord EX) so I want a radio that will
last me 20 years or more. This is what really led me to K3 as it can be
updated anytime. I have been looking at the SDR radios but I'm really a
"hands-on-the-knob" kind of operator. At field day I watched a ham at his
gigantic Flex 5000C and 23" monitor. Very impressive at first sight but
after watching for a while, I noticed that his entire operation was nothing
more than continuous wrist motions with the mouse. Just don't think I can go
there.

I hope to learn much more about the K3 as I bank away my extra dollars. It
looks like I need to buy quite a few of the options to do the K3 the way I
need (Ha-Ha: NEED) for my operations. Two meter board, ATU, DVR, a few
filters and the Panadapter are a must for me.

Here's my first question to the group:
I enjoy 6 meters immensely and someone recommended that I buy the pre-amp.
My understanding about the effectiveness of a VHF preamp is to amplify the
highest signal, i.e. at the antenna, to give the lowest noise increase. The
PR6 mounts at the radio. Wouldn't that be amplifying noise in a weak signal
more than if it were mounted at the antenna?

Thanks,
Larry
KB5HMU
http://qrz.com/db/KB5HMU
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[Tony Estep]

On Sun, Jul 3, 2011 at 1:02 PM, Larry, KB5HMU <[hidden email]>wrote:

> ...the K3 is at the top of my list...watched a ham at his gigantic Flex
> 5000C and 23" monitor.....continuous wrist motions with the mouse....

===========
Larry, this doesn't answer your question about the 6M pre-amp, but I would
make the following comment about the 23" monitor etc.

As an owner of both a K3 and a Flex radio, I'd point out that you can have
the best of both worlds by adding an LP-Pan and PSDR to a K3. I have exactly
the same 23" display on my K3 as on my Flex. And of course, I can click
around the band with the mouse just as I do with the Flex. You commented
that you like knobs and buttons, and so do I. The PSDR interface is okay for
zero-beat phone work, but I find it to be unsuited to working CW split.
Knobs and buttons are much better. You'll also find the K3 to be a better
performer all-around: a far superior ATU, better at digging out weak
signals, an incomparably superior keyer, etc.

Actually, there is a way to get an excellent physical interface to the Flex:
Tobias, DH1TW, has concocted a neat mod to the PSDR program that allows you
to use the Hercules MP3 DJ gadget to operate the radio. This sounds a bit
strange, but in fact it is wonderful. Not only does it overcome the foibles
of PSDR, but it turns out to be a really excellent ergonomic solution to
operating a ham transceiver. However, the Flex powers-that-be have offered
no encouragement or support to this splendid idea, so it has gotten traction
only with a small number of hard-core users like me. One of the great
reasons to own an Elecraft product is that the top guys are operating hams
who get on the air just like their customers do, and who listen and respond
to the needs and comments of users.

So get yourself a K3, and enjoy it for 20 years!

73,
Tony KT0NY
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[Edward R Cole]

Six meters at the boundary of HF to VHF characteristics.  Sky noise
still dominates on 6m with approx. 2000K noise temperature.  The PR6
noise figure reduces K3 sensitivity to -148 dBm (approx. NF of 2
dB).  That is a noise temp of 178K.

So if we add Tsky=2000K to Tr=178K and assume Tant=100K, the overall
system noise temperature is 2378K.
With a bw of 500-Hz this is a system sensitivity of -138.0 dBm.

If we add 1-dB coax loss from antenna to preamp, the sensitivity
drops to -137.8 dBm.  Not very significant change in sensitivity for
placing the preamp at the antenna.

I am installing a 6m eme station with 0.85 dB coax loss.  My preamp
is attached to the back of the K3.
http://www.kl7uw.com/K3-ARR-6mPreamp.jpg
http://www.kl7uw.com/6m.htm

73, Ed - KL7UW
------------------------------

Message: 12
Date: Sun, 03 Jul 2011 11:28:31 -0700
From: Alan Bloom <[hidden email]>
Subject: Re: [Elecraft] New to list; My first question
To: "Larry, KB5HMU" <[hidden email]>
Cc: [hidden email]
Message-ID: <1309717711.1754.27.camel@ulinux-desktop>
Content-Type: text/plain; charset="UTF-8"

On Sun, 2011-07-03 at 11:02 -0700, Larry, KB5HMU wrote:

 > Here's my first question to the group:
 > I enjoy 6 meters immensely and someone recommended that I buy the
 > pre-amp. My understanding about the effectiveness of a VHF preamp is
 > to amplify the highest signal, i.e. at the antenna, to give the lowest
 > noise increase. The PR6 mounts at the radio. Wouldn't that be
 > amplifying noise in a weak signal more than if it were mounted at the
 > antenna?

Yes, theoretically it is always better to put the preamp at the antenna
end of the feedline so that the noise figure is not degraded by the
feedline loss.  However, that is less of an issue on 6 meters than on
the higher VHF/UHF bands because:

(1) Coax cable loss is less at the lower frequency and

(2) Background noise is higher on 6 meters so that a super-low noise
figure is not as necessary.

It depends on what you're doing.  If you are into 6 meter moonbounce or
you have a long and/or lossy feedline then a remote preamp would be
worthwhile.

Alan N1AL







73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-100w, 1296-60w, 3400-?
DUBUS Magazine USA Rep [hidden email]
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