[Elecraft] Field Day rig experience

[Robert G Strickland]

Will...

A small nit... perhaps my ignorance... but, I think that the roofing 
filter [by whatever name] comes after the first mixer, at the so-called 
IF frequency. Your points are well made. I think the far out SDR's speak 
more to what can conceivably be done versus what's the design approach 
that best meets a broad range of desirable receiver parameters. Elecraft 
seems to have found the sweet spot in the battle of trade offs.

...robert

On 6/12/2018 15:49, WILLIE BABER wrote:
> More then one so2r operator has noted that the 7300 will overload in an so2r situation so that you cannot clearly hear on 7300 when the other radio is transmitting (yes, on a different band).  Since the 7610 doesn't have a front-end either, I imagine that it will do the same.  Sherwood himself notes that using the SDR radio (i.e, without a superhet front-end) means reducing gain to limit ADC overload, but he has also suggested that blocking dynamic range is over-rated.  Generally this is true, dynamic range is over-rated if you are using one radio.  However, blocking isn't over-rated in a field day situation (more than one radio) or if you have a neighboring op running high power, or in legal-limit multi-op situations (with antennas relatively close to each other), or in legal-limit so2r.
>
> Reducing sensitivity works to prevent ADC overload on the lower bands where sensitivity is not needed in the first place but on 15m through 6m one can use the sensitivity.  While SDR radios have their advantages, some of the advantages of superhet radios still exist today, namely, that a so-called roofing filter front-end (which is just a mode-specific filter ahead of the first mixer) will deliver outstanding blocking AND as much sensitivity as required (compared to SDR).
>
> I don't see any way around this fact (at least not yet) and you can see the difference in the Sherwood numbers.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA Advisor levels II and III
> http://cwops.org/
>
> --------------------------------------------
> On Sat, 6/9/18, Wayne Burdick <n6kr at elecraft.com> wrote:
>
>   Subject: Re: [Elecraft] Field Day rig experience
>   To: "Bill" <billclarke at nycap.rr.com>
>   Cc: "Elecraft Reflector" <elecraft at mailman.qth.net>
>   Date: Saturday, June 9, 2018, 10:34 AM
>
>
>   > On Jun 9,
>   2018, at 5:24 AM, Bill <billclarke at nycap.rr.com>
>   wrote:
>   >
>   > Along the
>   line (lightly discussed under "K3- AF Knob") of
>   what rigs are used for dxpeditions and Field Day......  How
>   do the new technology ICOMs (7300 and 7610) do under the
>   "several rigs on the same band" conditions? The
>   size, weight, and cost factor is inviting for the 7300 -
>   BUT!!! Is it up to the job? Close to up to the job? Or,
>   better left home during these events?
>
>
>   Hi Bill,
>
>   Hopefully you’ll get some responses to this
>   question from those with direct experience. But looking at
>   it theoretically: both the 7300 and 7610 are direct-sampling
>   radios with about 25-30 dB less blocking dynamic range than
>   the K3 or K3S. On Field Day this could have a definite
>   impact when using multiple transmitters on the same band, or
>   even on different bands, depending on antenna spacing and
>   power level used.
>
>   Dynamic
>   range of all of these radios is quantified in the receiver
>   performance table at www.sherweng.com, specifically the
>   fifth column (“100 kHz Blocking”).
>
>   Wayne
>
>
>
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-- 
Robert G Strickland, PhD ABPH - KE2WY
rcrgs at verizon.net.usa
Syracuse, New York, USA