Larry's LP-PAN uses my Z10000 amplifier design in its front end, with a
couple of modifications to provide variable gain.
The AD8007 amplifier chip in both my Z10000 and the LP-PAN is a decent
amplifier with a respectable noise figure.
If the K3's IF sample circuit had been built with closer to 0 dB
transfer gain, then the composite noise figure would be closer to the
K3's noise figure.
To answer the two questions directly (I don't have an LP-PAN, so Larry
might wish to modify my answers):
1. Is the mod necessary with the LP-PAN, or is it only needed with other
panadapters? That is, is the noise figure of the LP-PAN's internal amplifier
sufficient, or is the mod to the K3 required to lift weak signals above the
noise floor of the LP-PAN?
I believe you will see a small improvement in composite K3-LP-PAN noise
figure if the changes are made to the K3's IF sample circuitry. However,
I doubt that under most band conditions you will observe a difference as
there is sufficient external noise to mask the improvement.
2. Would the external buffer amplifier solution be a viable alternative to
the mod?
Yes, I believe it is if you are using something other than the LP-PAN as
the panadapter. Panadapters are not normally designed to be as sensitive
as a receiver. There are many reasons for that that I won't bother to go
over now. The consequence is that designers of receivers that provide a
pan scope RF sample have the levels set so that there is at least a net
0 gain, and positive gains of 10 dB or more are not uncommon. I'm
speaking mostly of commercial and military grade equipment, but my
Kenwood TS-940 has reasonable transfer gain as well.
Jack K8ZOA
www.cliftonlaboratories.com
Richard Ferch wrote:
I am scratching my head wondering whether any of this applies to the LP-PAN,
or whether it is only relevant to other panadaptors such as the Softrock and
the Z90.
K8ZOA's web page (the same one everyone is quoting) says:
"I looked at two potential panadapters; a Softrock and my Z90.
(Telepostinc's LP-PAN has a built-in amplifier to overcome the transfer gain
problem.)"
and in the recommendations near the bottom of the page, refering to the mod,
"These steps are not necessary with an LP-PAN panadapter as it has a
built-in isolation amplifier."
That same web page also suggests that an alternative to the mod would be to
use an external buffer amplifier.
So, I have two questions:
1. Is the mod necessary with the LP-PAN, or is it only needed with other
panadapters? That is, is the noise figure of the LP-PAN's internal amplifier
sufficient, or is the mod to the K3 required to lift weak signals above the
noise floor of the LP-PAN?
2. Would the external buffer amplifier solution be a viable alternative to
the mod?
73,
Rich VE3KI
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
