[Elecraft] preamp for using an SDR as a pan adapter

Fri Oct 4 20:59:33 EDT 2019

I knew I had an issue when I could hear signals on the K3s that weren’t
showing on the waterfall.

I need to engage Elecraft tech support to see if I need the mod for my K3s,
and see what they say about using an external buffer amp or preamp.

When I posted, I thought this might be a common problem that others had
fixed before.

On Fri, Oct 4, 2019 at 6:59 PM Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:

> I read that folks have successfully used the Clifton buffer amp.
> Certainly worth a try.   Others have indicated only about 6 dB of gain is
> needed.
>
> The software I use for my RSP-1 allows RF Gain changes.  Thus with the
> lower IF output of my K3S, I just raise the gain of the RSP-1 via the
> software.  I've never considered the SDR receivers of that type to be very
> precise with regard to "calibration".    Although some seem to think they
> can split hairs on a mosquito with the level and frequency accuracy of the
> receivers.    I do not consider them of instrumentation quality, thus
> anything +/-10 dB is deemed satisfactory.  Likewise the same with frequency
> accuracy.  Others may have different experiences with different receivers.
>
> 73
>
> Bob, K4TAX
>
>
> On 10/4/2019 6:34 PM, Fred Massey wrote:
>
> A friend of mine, Tim AB4B, suggested that I might need a buffer amp to
> keep the IF being pulled down by the sdr. DXEngineering sells the Clifton
> Z10000.  That adds about 6db of gain, but maybe the buffering that it does
> has an even bigger effect.
>
> On Fri, Oct 4, 2019 at 2:18 PM Bob McGraw K4TAX <rmcgraw at blomand.net>
> wrote:
>
>> In a word, YES.   I find that to be true with my K3S as well as other
>> brands/models of radios.   Thus you'll need about 20 dB of gain in the
>> form of a preamp between the IF output and the QSR receiver.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 10/4/2019 12:57 PM, Fred Massey wrote:
>> > Some.  I was planning on sending an email to Elecraft support with the
>> s/n
>> > of my K3s to see if I needed the mod.  The difference I’m seeing in
>> signal
>> > strength is about 20+ dB.  Is it normal for the if-out to be weaker
>> than a
>> > direct connection to the antenna?
>> > 73,
>> > Fred
>> > AE4ED
>> >
>> > On Fri, Oct 4, 2019 at 12:44 PM Don Wilhelm <donwilh at embarqmail.com>
>> wrote:
>> >
>> >> Fred,
>> >>
>> >> Have you looked the K3 IF Output mod?
>> >>
>> >>
>> https://ftp.elecraft.com/K3/Mod%20Notes%20Alerts/IF_Output_Buffer_Gain_Mod_Rev_A.pdf
>> >>
>> >> If you don't have the 13k SMD resistor or a 1/8 watt 13k resistor, you
>> >> can order the kit from Elecraft.
>> >>
>> >> 73,
>> >> Don W3FPR
>> >>
>> >> On 10/4/2019 1:24 PM, Fred Massey wrote:
>> >>> Good afternoon Wes and all,
>> >>>
>> >>> If I connect the antenna directly to the QSR-1, I get the same signal
>> >> level
>> >>> as the K3s.  But, when I connect to the QSR-1 to the IF-out, the
>> signal
>> >> is
>> >>> about 4 s-units less.
>> >>>
>> >>> Any ideas...anyone?
>> >>>
>> >>> Fred
>> >>>
>> >>> On Thu, Oct 3, 2019 at 4:14 PM Wes <wes_n7ws at triconet.org> wrote:
>> >>>
>> >>>> I use an SDR-IQ on the i-f output on my (very) early K3S.  it works
>> >> fine.
>> >>>> IIRC,
>> >>>> always a dubious proposition, I did the mod on my original K3 and it
>> >>>> worked well
>> >>>> too without any additional amplification.  I think you have another
>> >>>> problem.
>> >>>>
>> >>>> Wes  N7WS
>> >>>>
>> >>>> On 10/3/2019 2:01 PM, Fred Massey wrote:
>> >>>>> Good afternoon,
>> >>>>>
>> >>>>> I have successfully connected my QSR-1 to my K3s if-out, and
>> >> immediately
>> >>>>> noticed the signal strengths showing on the QSR-1 were much
>> weaker.  I
>> >>>>> probably have an early K3s, so the if-out signal strength is even
>> >> weaker.
>> >>>>> Any recommendations at a good preamp to use?  It seems like 20db is
>> >> what
>> >>>> I
>> >>>>> need:
>> >>>>>
>> >>>>> 73,
>> >>>>> Fred
>> >>>>> AE4ED
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