[Elecraft] Filter problems

[Vic K2VCO]

I don't have a 250 Hz filter, but both of my 400 Hz ones do require a few dB. I am more 
surprised that your main filter requires NO boost, than that your sub requires 6 dB. How 
much do others who have 250 Hz filters use?

On 4/3/2013 6:32 PM, Jim Miller wrote:
> I spent some time last night playing with various filter settings via the K3 utility. 
> What I found is that the 250 8p filter in the main required no boost to maintain signal 
> level as I dialed down the bandwidth and engaged it. The suspect one in the subrx 
> required 6db of boost.
> Has anyone else seen this level of boost required?
> With the subrx bandwidth increased to be just above its 250hz8p filter the receiver 
> comes alive nicely.
> I'll open up the K3 this weekend and do a filter inspection to see if there is some crud 
> on the pins and try a filter swap to the main just to verify my suspicion of a bad filter.
> I may have to order another...
> jim ab3cv
>
>
> On Wed, Mar 27, 2013 at 12:55 AM, Vic K2VCO <k2vco.vic at gmail.com 
> <mailto:k2vco.vic at gmail.com>> wrote:
>
>     Make sure the filter gain compensation is set properly for the 250 Hz filter. The
>     easiest way to do it is from the filter configuration screen of the K3 utility.
>
>
>     On 3/26/2013 5:44 PM, Jim Miller wrote:
>
>         Just used the K3 utility to disable the 250 8p on the sub and the audio now
>         is balanced regardless of sub bandwidth. Of course the noise level changes
>         but no imbalance with strong or weak sigs between the two.
>
>         Now to figure out if it's the socket or the filter at fault.
>
>         jim
>
>         On Tue, Mar 26, 2013 at 8:22 PM, Jim Miller <jim at jtmiller.com
>         <mailto:jim at jtmiller.com>> wrote:
>
>             I think I've figured out why my subrx seems to be much less sensitive than
>             the main. I was playing around with the bandwidth control today while
>             having the VFOs linked.
>
>             I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
>             pole. I have both main and sub set to cut to the 250 at 350hz. I do most of
>             my Dx activity with the BW set to 350 so engaging the 250hz filter.
>
>             What I noticed is that although the sub is much less sensitive than the
>             main with the 250 engaged it is just fine just above where the filter kicks
>             in.
>
>             This tells me that something is wrong with the filter or the socket it is
>             in. The balance control has to be set past 3 oclock to even out the signals
>             with the 250 engaged in the sub. The balance is just fine however when that
>             filter isn't engaged.
>
>             I'm going to try moving the filter to another socket in the sub to see
>             what effect that has.
>
>             I can also try swapping the 250 between the sub and the main to see if the
>             loss of sensitivity tracks the filter placement.
>
>             Any other ideas?
>
>             It could be a bad filter. I don't think the filters should be that
>             different in loss when in spec.
>
>             jim
>
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>     -- 
>     Vic, K2VCO
>     Fresno CA
>     http://www.qsl.net/k2vco/
>
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/