[GCARC] 2:1 SWR

Thu Jun 6 13:09:59 EDT 2024

Looks like a lot of people were listening to last night's session! Also looks like we should keep Spenser on our active presenters list for another future session.

At the end of his presentation he brought up Smith charts which suggests a good Tech Saturday session, possibly in August. Many hands were raised at the meeting when that was suggested but if you're particularly interested please let me know. Also let me know if you have suggestions for subsequent Tech Saturday sessions since we don't have topics lined up after June.

73 de Jon WB2MNF

-----Original Message-----
From: gcarc-bounces at mailman.qth.net <gcarc-bounces at mailman.qth.net> On Behalf Of Kenneth Bozarth
Sent: Thursday, June 6, 2024 11:29 AM
To: Tony Starr <tstarr1450 at gmail.com>
Cc: gcarc at mailman.qth.net
Subject: Re: [GCARC] 2:1 SWR

Right on, Tony. And I didn't mention that you do not see massive heat sinks in these new rigs anymore. They figure that a slab of metal with a small fan are good enough. Shame on them! They are playing the odds that we listen most of the time, don't talk long and most of us have tuners. I'll take a pair of 2SC2879s any day.

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On Thu, Jun 6, 2024 at 11:13 AM Tony Starr <tstarr1450 at gmail.com> wrote:

> While it may be true that solid state final amplifiers with fixed
> tuning for a 50 ohm system have some degree of mismatch capability,
> keep in mind that even a perfect antenna may not be 50 ohms resistive.
> A perfect dipole of around 70 ohms as well as a perfect ground plane
> vertical of around 35 ohms will start out at close to 1.5 to 1 at band
> center, and will only get worse as one moves out toward the edges of
> the band. This is why built-in tuners became a standard feature in solid state radios in the first place.
>
> I agree with the presenter that the equipment manufacturers are doing
> us a great dis-service by not building in enough working mismatch
> range into their equipment.  They are likely doing this to cut down on
> size, weight, and cost; and not just in the output devices, but with
> all of the ancillary components that make up the final output stage.
> Solid state transmitters, as good as they are, still have significant room for improvement.
>
> de K3TS
>
> On Thu, Jun 6, 2024 at 9:46 AM Karl Frank W2KBF via GCARC <
> gcarc at mailman.qth.net> wrote:
>
> > To followup the topic of antenna matching/SWR from the meeting last
> night,
> > I
> > looked up the recommendations from ICOM and YAESU for two of my HF
> > rigs that do NOT have an internal tuner.
> >
> > For the IC-7100, ICOM recommends an SWR less than 1.5:1 and says
> > that
> power
> > foldback will occur with an SWR greater than 2:1.
> >
> > For the FT-891, Yaesu recommends an SWR of less than 1.5:1 and does
> > not mention power foldback.
> >
> > So Chris AD2CS was correct to question the statement that any SWR
> > less
> than
> > 2:1 is no problem.
> >
> >             Karl W2KBF
> >
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