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

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