05-11-2017, 03:59 PM
Wayne
After my last caravan trip, I set about building up a multiple ratio UN-UN to use with my 7M long wire squid pole style antenna. I used a FT140-61 toroid with quadrifilar windings and where the joints between the windings are, those points were taken to separate connection point screws on the ABS box housing. That gave me ratio points of 4:1, 9:1 and 16:1 that I could attach the antenna wire end to via a crocodile clip. The earthy side of the assembly connected to the coax connector and thence to the caravan frame via a second croc clip and braid.
I tried measuring the impedances on the various bands using my homebrew Z-analyser and squid pole wire and determined which ratio tap would work best on any particular band by looking for a resistive component between 10 and 100 ohms coupled with as close to a zero reactive component. That gave me starting points for all bands 80 metres to 10 metres, WARC bands included. I couldn't get anywhere near a satisfactory outcome on 160 metres, and 80 metres was questionable.
Next I used my IC706Mk2G via an LDG Z100 autotuner into the UN-UN and repeated the tests band by band. The setting as to whether the tap was 4, 9 or 16:1 was less critical as the autotuner adjusted for each band but I couldn't achieve a match on 160 metres regardless. The autotuner did match on 80 metres though I have doubts as to how efficient the antenna would actually be there.
I haven't done exhaustive tests to see how effective the UN-UN and 7 metres of wire(/squid pole) are as an antenna assembly but will probably see how it goes on my next bush outing, somewhere where it is quiet and isolated. I have added a trapped-wire arrangement to the portable kit so it is an alternative to the squid pole/UN-UN and it covers 80, 40, 20, 15 and 10 metres (using 4 homebrew traps on PVC pipe). It is (again) run against the metal caravan frame but only needs to be elevated at one end, and clips to the centre pin of a coax panel socket connector, the outer frame again via a braid and croc clip to ground (no BAL-UN or UN -UN). In essence it is just half of a trapped dipole but is light and easy to erect and operates on the 5 most likely bands. Most of the details are similar to the design described at http://www.vk4adc.com/web/index.php/hf-p...v-v-for-hf. If I recall correctly, the total length was about 10 metres (for the one side) so that is close to your target of 10 metres, do-able if you slope it a bit such that it is close to the mast at the top and spaced out at the base. You can also add traps to make it operate on 10, 18 and 24 MHz if you want to. Worth a thought.
73 Doug
PS My 19 metre length of wire tunes well on 80 metres, but then again it is about 1/4 wavelength..
After my last caravan trip, I set about building up a multiple ratio UN-UN to use with my 7M long wire squid pole style antenna. I used a FT140-61 toroid with quadrifilar windings and where the joints between the windings are, those points were taken to separate connection point screws on the ABS box housing. That gave me ratio points of 4:1, 9:1 and 16:1 that I could attach the antenna wire end to via a crocodile clip. The earthy side of the assembly connected to the coax connector and thence to the caravan frame via a second croc clip and braid.
I tried measuring the impedances on the various bands using my homebrew Z-analyser and squid pole wire and determined which ratio tap would work best on any particular band by looking for a resistive component between 10 and 100 ohms coupled with as close to a zero reactive component. That gave me starting points for all bands 80 metres to 10 metres, WARC bands included. I couldn't get anywhere near a satisfactory outcome on 160 metres, and 80 metres was questionable.
Next I used my IC706Mk2G via an LDG Z100 autotuner into the UN-UN and repeated the tests band by band. The setting as to whether the tap was 4, 9 or 16:1 was less critical as the autotuner adjusted for each band but I couldn't achieve a match on 160 metres regardless. The autotuner did match on 80 metres though I have doubts as to how efficient the antenna would actually be there.
I haven't done exhaustive tests to see how effective the UN-UN and 7 metres of wire(/squid pole) are as an antenna assembly but will probably see how it goes on my next bush outing, somewhere where it is quiet and isolated. I have added a trapped-wire arrangement to the portable kit so it is an alternative to the squid pole/UN-UN and it covers 80, 40, 20, 15 and 10 metres (using 4 homebrew traps on PVC pipe). It is (again) run against the metal caravan frame but only needs to be elevated at one end, and clips to the centre pin of a coax panel socket connector, the outer frame again via a braid and croc clip to ground (no BAL-UN or UN -UN). In essence it is just half of a trapped dipole but is light and easy to erect and operates on the 5 most likely bands. Most of the details are similar to the design described at http://www.vk4adc.com/web/index.php/hf-p...v-v-for-hf. If I recall correctly, the total length was about 10 metres (for the one side) so that is close to your target of 10 metres, do-able if you slope it a bit such that it is close to the mast at the top and spaced out at the base. You can also add traps to make it operate on 10, 18 and 24 MHz if you want to. Worth a thought.
73 Doug
PS My 19 metre length of wire tunes well on 80 metres, but then again it is about 1/4 wavelength..
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
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http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.