[Elecraft] Band pass filters

[Dave]

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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>>
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