Hi, Brent, Mark
Brent, I received your earlier direct email, but much has been going on,
and then there was Florence to harass us here in NC. Locally, Florence
washed out my next door neighbor's driveway. Reedy Branch (a tiny tributary
of the Cape Fear) runs under both our driveways. I have a 54 inch culvert
pipe, and neighbor had a 40 inch. My pipe was carrying water to the top of
the pipe, and his could not keep up, over and under-washing his pipe eating
an 8 foot deep, 8 foot wide ditch in his driveway. We had to make a way for
him to drive between our houses to get to our driveway. Things will still
be a bit weird around here for a while, so please be patient. Some
correspondence may not be answered for two or three weeks. No way to avoid
that.
I also received an auto-reject message on an earlier (today) answer from
Mark, K5LXP about the nature of the modification to the relay. (Mark, you
are subscribed with an address with your callsign in it and you sent from
an address that begins with "qrq". Please update/replace your
subscription.) I have inserted the text from Mark's post:
-------------------------------------------------------------------------------------------
From: Robert Scott via Antennaware <antennaware@contesting.com>
> IN the K2AV page on the FCP+ there is a comment about modifying a DPDT
relay
Judging by the text it sounds like bridging the wipers of a multi contact
relay to achieve a cumulative increase in contact gap. I did that with an
antenna switch using relays to improve isolation and return loss. Stands
to reason it will increase voltage rating as well. Found an illustration
of it here:
<https://www.qsl.net/ei7ba/images/Remote/Relaymod.GIF>
Mark K5LXP
Albuquerque, NM
-------------------------------------------------------------------------------------------
The illustration properly describes the changes to the relay's internal
wiring, which converts it to a shorting-bar relay. The pole pins on the
base are no longer attached to anything. With power off the two normally
closed base pins on the base are shorted. With power, the two normally open
base pins are shorted.
The modification to the Deltrol is to slightly bend the normally closed
upper contacts (not the blades) to obtain an 80 mil gap between the blade
contacts and the normally open contacts. Then remove the wires from the
blades (poles) that come around from the back to the base pins. Then solder
a short between the blades behind the support (opposite side from contacts).
The illustration above does not include increasing the gap.
Regarding the other relay manufacturer: From various photos around the
internet of the JQX-12F 2Z, it seems plain that it's designed/tested to a
max of 600 VAC and would not withstand high voltage RF. The internal base
is different and lacks some helpful insulating features of the Deltrol
parts. Therefore our use of them at RF would require careful examination.
The Deltrols have been sold by Array Solutions for a while and I've not
heard of troubles. But I'm sure that the use we are proposing has not been
inflicted upon that model.
It seems that the tariffs/trade wars have effectively removed Deltrol brand
(Chinese) from some American suppliers (like Mouser). or raised the price
at others. Array solutions can still get them, but it is clear their
acquisition costs are up, and they've raised their price to cover (31 bux).
Allied Electronics has them for 21 bux, see
https://www.alliedelec.com/deltrol-controls-20852-81/70733570/ These *used
*to go for about 12 bucks from Allied and others. I suspect that many are
using the trade fracas as an excuse to raise prices to the degree I've
seen.
The big problem with finding a manufacturer with an appropriate
replacement, is that you need good pictures of the relay to see if you can
fudge it by converting it to a bar short across the NO or NC contacts. It
took me weeks to find the Deltrol 20852-81. But series 80 mil separations
was only good for 6 kVDC. it took 4 kV to clear the first gap, but only 2
kV more to clear both gaps in series. That's an oddity I was not expecting.
The air gaps figure one sees over and over calculate to 160 mils should be
good to 12 kV DC, which is enough.
We do not know if the hipot tester is calibrated or linear on the meter. I
do NOT know if RF breakdown behaves the same as DC breakdown. When I am
done with some prerequisite construction, I will actually trying out the
modified relay up on the FCP, to see whether and at what power it breaks
down. I can go up to about 2000 watts .
Until then, I simply do not have anything solid to put on the web page,
other than minimum 12 kVDC rated vacuum relay. The working 80/160 dual band
L/FCP (all QRO) I know of are all using a vacuum relay for the FCP short
function. Most of those are also using a vacuum DPDT relay for the tuning
side switching for low end 80 and low end 160.
I would point out to those who are bothered by the cost of an appropriate
vacuum relay, that it's a small fraction of the cost of a transceiver, and
that spending money on an antenna that really works is worth it. I already
have a Kilovac H-9/S21 which is an SPST rated 15 kV. However it's *normally
closed*, which means that the no power state is 80 meters. I want the power
off setting to be primary range on 160, not 80. At Surplus Sales of
Nebraska I found a Jennings RD5A, also rated 15 KV but normally open. Not
quite 100 bucks by the time intra-USA shipping and tax added. I'll test the
modified Deltrol first but switch to the vacuum later. I may put both
relays in the same box in series, with separate coil leads to the shack, so
I don't have to be off the air if/when the Deltrol arcs over on 160.
With the price increases, 20 or 30 bucks for the Deltrol, *and *you have to
modify it and possibly operate restricted power, hardly seems worth it as
long as you can buy RD5A's from Surplus Sales for 100 bux.
73, Guy K2AV
On Tue, Sep 4, 2018 at 2:56 PM Robert Scott <wr5o@icloud.com> wrote:
> Thank you so much or all of your hard work on the LFCP. I am going to
> attempt the 160/80 meter version and have a question:
>
> "A simple modification to the shorting DPDT relay produces a doubly
> isolated SPST shorting relay for the FCP with .160 inch (4 mm) of total
> contact gap space."
>
> What is the modification for this? Also, what are your thoughts on using
> this one from amazon?
>
>
> https://www.amazon.com/gp/product/B008MU0MRQ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
>
> Regards
>
> Brent Scott
> WR5O
>
>
>
_______________________________________________
Antennaware mailing list
Antennaware@contesting.com
http://lists.contesting.com/mailman/listinfo/antennaware
|
