VK Logger Ham Radio Forum Archive

Hi guys

A mate and I are wanting to make the 20m coil to suit the VK7JJ squid pole antenna as described here http://www.perite.com/vk7jj/squidpoles.html but we haven't had much luck finding a source for the high voltage trim caps required to make the coil.

My mate tried Rockby as mentioned on the VK7JJ site but they don't sell them anymore. We also tried AZtronics but they don't have anything capable of handling 100 watts.

Can anyone help?

You could talk to Alex http://www.ur4ll.net/#caps4 but some pc board and rubber bands works rather well (single sided) is good for the limit

Hmmm. I'll have to look into this one.

Valve radios generally have something suitable on the tuning gang or in the changer section. They might be a bit bigger than required but you could always trim the plates with a set of shears. PCB is a good alternative.

Hi, How about using RG213 or similar? 12 inches is around 31pF. Simply attach the braid and centre conductor across the circuit where a capacitor would sit and trim the open end for resonance. When tuned, place a heat shrink cap over the open end. Cheers, Paul

25pF beehive trimmers are commonly found in VHF FM transceivers common at hamfests. Given that they're OK for 25-30w FM they should be OK for 100w SSB.

For example http://www.ebay.co.uk/itm/10-x-PHILLIPS ... ltDomain_3

Mica compression trim caps are getting harder to find these days, especially locally.

There are places in the US that have them eg: https://www.surplussales.com/Variables/ ... pCap1.html

Terry

VK5MTM wrote:Can anyone help?

It has been several years since I built my squid pole antenna however I seem to remember that I bought my caps from the local Jaycar store. Whether they still have them tho I do not know.

73
John

VK7DB wrote:http://www.sgcworld.com/237ProductPage.html

That's a really BIG trimmer.

It works very well on the end of my 7JJ inspired squid pole, but I'm just lazy..

When you buy one of these fishing rods is that "squid pole quo? "

Ebay item 361194836050 looks really interesting

Where's the home brew spirit?

30pf is, how many square inches of 1/16" PCB?

Building damp course aluminium strip is handy stuff, 30cm x 10m roll from Bunno's.
Much more robust than kitchen al-foil.

200mm piece of 40mm PVC pipe, foil inside to 1/2 way down. held out with sponge. (the hot end)

Sliding up and down, a 100mm piece on the outside. (the GND end)

**** Test your PVC pipe in the microwave oven with a glass of water, if the PVC gets hot choose another type ****

100W at 2MHz (Marine band) can generate high RF voltages. I saw 1/2" arcs and many burnt relays. (RACAL 7948s in 1974)

**** RACAL here in Australia did the 1st 100W fully solid state HF (2-8 MHz) radios in the world in 1966. ****
See one at Kurrajong.

Alan VK2ZIW

Could you use a foot of RG58 to get the capacitance? A bit like how some traps for trapped dipoles are made.

VK3MIX wrote:Could you use a foot of RG58 to get the capacitance? A bit like how some traps for trapped dipoles are made.

Yes. Maybe with the ends frayed then soldered so you could move them and get a few pf variation.

Or bits of circuit board material slid over one another.