[1000mp] Mark V Front-End Amp Setting.

[George, W5YR]

The short answer is that filters have insertion loss. When they are switched
in with "tuned" the insertion loss evidently is about 6 dB.

I would expect that the IF gain would be automatically increased to
compensate for the filter loss, but evidently not so.

Not using the filters is trading some protection against spurious signals
for sensitivity. As you point out, on the lower HF bands, external noise
will set the noise floor and any added gain is probably wasted. Thus, it
would seem the best strategy to operate in "tuned" mode and get the benefits
of those front-end filters for the ham bands.

73, George W5YR
w5yr@att.net


----- Original Message ----- 
From: "WX5L" <wx5l@charter.net>
To: <1000mp@mailman.qth.net>
Sent: Friday, December 12, 2003 8:10 AM
Subject: [1000mp] Mark V Front-End Amp Setting.


> Hello,
>
> I wanted to share this observation I recent made with my Mark V.
>
> With a signal generator I injected the theorical s-9 signal level of -73
> dbm. Indeed the s meter read s-9 on all bands. I've always set my receiver
> front-end to "tuned" in menu 8-4 but as a curiosity test I switch to
"flat"
> and found a slight increase in sensitivity as indicated on the s-meter of
> about 6 db. Not much really but could make the diffference under very weak
> signal situations.
>
> I would have thought in the 'tuned" setting and having seperate tuned
> amplifiers for the low and high bands I would notice higher gain but that
> was not the case.
>
> This slight increase would probably be unnoticable with on-air copy due to
> qsb ect but with a steady signal it was obvious.
>
> This was not a sophisticated testing procedure and the results were
contrary
> to what I thought.
>
> 73,
> Randy
> WX5L@charter.net
> Thibodaux, Louisiana
>
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