Re: FDM-DUO overload issues

Wesley Knox

Steve, I have the QSF-06 and bought just about all the bandpass filter boards as an insurance policy against front-end overload issues.  I don’t have strong-signal overload issues as I’m somewhat rural but nearby hams don’t cause any problems for receiver.  Yes, not cheap but I did want zero problems after investing the amount of cash in the system.  On the negative side, I’m annoyed by the flat cable interface with the ELAD mounted on the FRONT of the device.  It spoils the esthetics of the installation since you’d like to view the cute little blue LEDs denoting the band it’s selecting.  The QSF also has a 3.5mm jack, again on the front, that provides a DC signal to communicate to other gear (like an amplifier for instance) the band selected.  I have a Hardrock50 amplified which accepts a DC level to automatically bandswitch itself and the internal ATU.  The QST-supplied DC levels are identical levels to those used by the amp (and I believe other devices as well).  I did not need to use the amp interface from HobbyPC to provide this, I just wired a 3.5mm plug to a DB9-P with RG-170 coax and it does the trick.  Anyway I have not evaluated the QSF with a lab sig-gen to determine its overall effectiveness/specs, I just don’t encounter ADC overloads (unless I disable the AGC function).  I experimented with the attenuator function when I received the rig but have never used it in anger.  I am somewhat mystified by the AGC Threshold (Thr) level slider on the SW2 software.  I functions like a reverse-RF gain control instead of a level-set for cutting off audio (like a squelch level).  Anyway, no matter, I rarely use it at all.  The Noise Reduction slider also reduces noise level as well.  On the QSF-06 subject, there’s enough room in the unit to gen up multi-pole(and zero) passive or even active filtering so overall I felt it would be a good investment since I’m not one of those perennial rig swappers/upgraders.  Good luck with the rig, I spent 40+ years in electronics/computers and just love the SDR and its performance…until the next gotta-have unit appears.







From: <> On Behalf Of Steve Knell
Sent: Wednesday, May 27, 2020 1:12 PM
Subject: Re: [EladSDR] FDM-DUO overload issues


Yes, I see the PK flashing at times particularly on 80/40 but more recently on 20M because I have improved my antenna setup.  I only use the ham bands and I have no nearby AM broadcast transmitters.  I don't want to criticize the FDM-DUO because it's done a superb job for me and you get what you pay for.  No-one could expect it to compare with one of the high-end $4000 radios.

I was just on in the CW-Ops activity hour on 80/40/20 and I could hear the low level sqwauk of a strong stations on 40M, but I forgot to check the PK indicator at the time.  I've had the Elad for several years and I hadn't even noticed the PK indicator until I started to research ADC overload..!

During the day there is some local electric fence noise - not sure if that is a contributing factor as well, on 20M.

I would be interested to hear from anyone who has that QSF unit and whether it has helped them with ADC overload on the ham bands.


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