[600MRG] Some experimenting with toroids vs hollow coils on 630m

[D.J.J. Ring, Jr.]

Oops! I read it back asswards. I read it wrong. The toroid was 10 dB worse
than the hollow coil.

Did the hollow core have any ferrites? Or was it just a PVC pipe?

How did you make the hollow core?

Regards,

David

On Wed, Feb 15, 2023, 22:18 D.J.J. Ring, Jr. <n1ea at arrl.net> wrote:

> This is what you found better:
>
> https://www.ebay.com/itm/153981039085
>
> Have you tried any of the other core materials. I'm guessing that the
> FT240 is the heaviest duty torroid they make and what's after the
> hyphen is the core material.
>
> I see others but all are less expensive, but you probably went first
> class and for 10 dB it sure is worth it.
>
> 73
> DR
>
> On Wed, Feb 15, 2023 at 9:51 PM Neil Klagge <w0yse at msn.com> wrote:
> >
> > The following is just my experience, not a scientific thesis  😉
> >
> > These are the results of an experiment comparing a FT240-52 with a
> hollow cylindrical coil on the ouput of my 630m IRF510 FET power amplifier
> for 630m.
> >
> > Transmitter output was 4.5w input to the toroid for this test, but there
> was only 2w left on the output of the toroid, going into the coax to the
> antenna. The KA7OEI-1 Northern Utah SDR was used during midday to decode my
> signal with that core. The results were worse by about 10 dB compared to
> when using the hollow PVC coil. The amplifier ran very warm with the toroid
> even though my fans were running full blast and even though the SWR was
> very low.
> >
> > Using the same output power of the amplifier, the cylindrical coil got a
> 10 dB stronger report from the SDR.  And, there was negligible heating of
> the amplifier.   (I had similar results with an FT240-43 core the previous
> week).
> >
> > The #52 core is less than 45% efficient whereas the PVC coil is about
> 83% efficient. The PVC coil wins!
> >
> >
> >
> > Next, I experimented with the 52 core at the base of the antenna. I was
> able to get the SWR under 2.0 at the base of the antenna by adding or
> subtracting turns on the core. Inside the shack I could adjust the SWR to
> about 1.2 but the amplifier still ran hot when using the toroid and the
> reports back from the N. Utah SDR were weaker by about 7 dB.
> >
> > My original coil at the base of the antenna works much better than the
> 52 core.
> >
> > Hoping some will find this useful...
> >
> > 73
> >
> > *´¨)
> > ¸.•´¸.•*´¨) ¸.•*¨)
> > (¸.•´ (¸.•`   Neil , wØyse, DN41ah, North Ogden, Utah 84414
> >
> >
> > My ham radio website: http://w0yse.webs.com/
> >
> > My Faith website: http://neilsfaith.webs.com/
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