Bird makes a very good bandpass filter for the SDR radio you are
speaking of... It gets rid of ALL phase noise on all bands at once.
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 7/27/21 12:50 PM, Bill Steffey NY9H wrote:
well said....
at field day that famous SDR, very reasonably priced, abundant with
features DID INDEED SPREAD wide band noise ..it was on 10 and wiped out
all thru 80 meters on three other radios of various makes. ( mine was a
k3) ...
maybe all we needed was to have bandpass filters for THAT radio ... but
4 band of good filters starts to move into the purchase price of that radio
Sherwood has spoken of this...and hope he will be elaborating ... as
I hate being the bearer of bad news....
bill ny9h
On 7/27/2021 2:49 PM, David Hachadorian wrote:
You need a filter on the TX radio to prevent its phase noise from
being heard on other bands. Just pressing PTT on the TX radio, even
without putting out any measurable power, will raise the noise floor
on multiple bands. With suitable band decoders driving filter
selection, fast-switching between bands is possible.
Dave Hachadorian, K6LL
Yuma, AZ
On 7/27/2021 9:09 AM, CUTTER DAVID via Elecraft wrote:
Given the improved performance of modern transceivers, is there still
a call for high specification W3NQN band pass filters in a
2-transmitter station? For example on a Multi-2 contest
environment. For instance K3S + KPA + KAT. The filter fitted between
radio and amplifier.
I have the *feeling* that a receive-only filter (with tx bypass)
might be all that is needed. This is much easier to implement than a
full transmitter-rated set making fast switching between bands (eg
for a quick look around) very quick and easy from the keyboard, etc.
David G3UNA
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