A 10m Vertical Dipole Array for T2GM I built and tested. This followed dimensions provided by DJ2YA and needed very little adjustment, constructed with 1.2mm bare copper wire. Sorry about the picture, was a very grey winter afternoon. See VSWR sweep below.
I needed to build some small baluns for vertical dipoles and arrays, to be used on the T2GM dxpedition. We required the following:
- Handle 500w
- good choking impedance 14 to 30Mhz
- Lightweight and waterproof
First I tried a W1JR type on a FT140-43 core. This was a nice balun, but was not easy to form even with thin teflon coax and the performance dropped off on 10m. After reading GM3SEK’s article I headed to the junkbox to see what other ferrite I had to hand. I have a good number of Ferroxcube CST19/10/29-4S2 cores which I picked up on ebay for a song. 4S2 material is very similar 43 material.
Two cores were glued together to form a binocular, 3 turns of RG316 teflon coax fits through neatly. RG316 is only 3mm diameter but can handle 1.1Kw on 10m! The choking impedance is > 2000 ohms 14 to 30Mhz, reaches 2550 ohms on 10m. This was fitted into a small 60 x 65mm polycarbonate waterproof box with a 6m flying lead of Aircell 5 coax.
Two identical baluns were connected back to back and tested for extended periods 500w key down. Both the cores and the RG316 coax became warm as you would expect, but nothing to get worried about. I am confident they will survive anything when used at this power level.
I have completed the 6X2 7/16DIN switch and works as expected. Mike has done a great job with the design and the PCBs are excellent quality. The case is made by Rose Bopla p/n 012328118, available from Digikey. Rather expensive but perfect for this project. Measurements made with my N2PK VNA :
Insertion Loss Radio 2 <=> Port 6 0.066dB @ 28.477 Mhz
Return Loss Radio 2 <=> Port 6 24.5dB @ 28.477 Mhz
My old Sixpak was showing its age so I decided to replace. SM2WMV offers excellent PCBs which make homebrew easy, the 7/16 DIN version ideal for me as I have a box of used connectors for Andrew LDF.
Its almost complete, just need to fit the series inductors and test.
Tribander on a roof on Murano Island, Venice. Nice blue glass sculpture across the canal from his qth. Murano is just one big glass factory.