RE: the high price of coils...Imagine what "they" are charging the
government
for those coils! Our tax dollars at work. It's like the $600 toilet
seat made
for aircraft....heh..heh, remember that fiasco?
Charlie, N0TT
On Mon, 4 Aug 2025 15:07:28 +0000 Bill Eisinger <Bill@theeisingers.com>
writes:
> I was one of the first purchasers of Gaylord's (N4SF) coils...they
> are very well made and really the only option out there these days
> if you need large inductors. He also sells some nice clips for
> finding the tap point you need that can be tightened with a screw to
> make a semi-permanent connection.
>
> In my search for coils, I contacted B&W...they are still in business
> but sell almost 100% to government purchasers but will do custom
> orders with a minimum run of 10 units...that sounded OK...I figured
> I could buy 10 and recoup my money by selling the extras... until
> they quoted me a price of $33,000!
>
> Bill, AA7X
>
>
> ________________________________
> From: TowerTalk <towertalk-bounces@contesting.com> on behalf of
> Brian Beezley <k6sti@att.net>
> Sent: Monday, August 4, 2025 8:44 AM
> To: towertalk@contesting.com <towertalk@contesting.com>
> Subject: [TowerTalk] Loading Coils
>
> "FWIW, your number for Q (673) agrees exactly with the number I get
> using Medhurst's 1947 formula."
>
>
> Interesting, Rick. I'm surprised you got the same result. I've
> tried
> several methods of calculating coil Q. Skin depth is
> straightforward.
> The proximity effect is another matter. I wound up using an
> integral
> equation developed by G3RBJ. I modified an approximation it uses
> for
> slightly better accuracy. The method yields the most accurate
> results
> for the set of test coils I measured with my HP 4342A Q meter.
>
> Q is not easy to accurately measure for big coils like those sold
> by
> QCoil. The fields may extend quite a distance and interact with
> nearby
> objects, such as the instrument enclosure or even your body. The
> Qcoil
> photo shows the coil quite close to the HP 4275A. I wrote a utility
> to
> let you remote a coil with a transmission line to minimize
> interaction.
> The program recovers coil inductance and Q from what a Q meter
> indicates
> for a remoted coil. The program is part of my Q meter utilities
> listed
> near the center of this page:
>
> https://k6sti.neocities.org/mu
>
> I verified that the tiny zeros in the HP instrument do mean that
> the
> digit is not necessarily accurate. So 6oo means Q is closer to 600
> than
> to 500 or 700.
>
> It turns out that QCoils is just a few miles away from me. I'm going
> to
> contact the owner to see if he will loan me some coils that I can
> measure with my HP 4342A.
>
> Brian
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|