{"id":3444,"date":"2021-04-08T05:05:00","date_gmt":"2021-04-08T09:05:00","guid":{"rendered":"http:\/\/w4kaz.com\/qth\/?p=3444"},"modified":"2021-05-06T22:38:55","modified_gmt":"2021-05-07T02:38:55","slug":"end-fed-half-wave-experiment-part-4","status":"publish","type":"post","link":"http:\/\/w4kaz.com\/qth\/?p=3444","title":{"rendered":"End Fed Half Wave Experiment – Part 4"},"content":{"rendered":"\n
EFHW Experiment Part 1<\/a>
EFHW Experiment Part 2<\/a>
EFHW Experiment Part 3<\/a><\/h5>\n
UPDATED 2021-04-08
Transformers???<\/h5>\n

On a whim I decided to wind a transformer using two FT-140-43 cores.\u00c2\u00a0 I went with the same 2:1 ratio as the first transformer.\u00c2\u00a0 SWR testing using this second version showed that all transformers are not equal.\u00c2\u00a0 The SWR readings taken using the new transformer with the antenna wire as it was trimmed with the larger transformer did not have similar results.\u00c2\u00a0 It turns out the new transformer would require re-trimming the wire lengths to bring the 40m band into the same SWR curve.\u00c2\u00a0 Since I had the 80m coil&tail attached using .250 quick connects, it was easy to add wire.\u00c2\u00a0 Doing that allowed bringing 15m and 10m to good matches.\u00c2\u00a0 20m also found a sweet spot but only on the 6.5:1 tap.<\/p>\n

New Version?<\/h5>\n

Without re-tuning the wire no good matches were obtainable on 40m.\u00c2\u00a0 Instead of making any permanent changes to the working 40m loaded antenna\/transformer combo I am making a different wire based on a 30m wire length.\u00c2\u00a0 It will include a quick connect to allow the antenna to cover 20m by detaching the section of wire beyond the ~34 foot 20m wire length.\u00c2\u00a0 That will provide an antenna capable of 30m\/20m\/15m\/10m.\u00c2\u00a0 This may become a simple way to add a permanent 30m antenna in the w4kaz antenna farm.\u00c2\u00a0<\/p>\n

Maybe I get ambitious and add a second link to include 17m, just for grins.\u00c2\u00a0 Does an easy tune 30m\/20m\/17m\/15m\/10m antenna sound good?\u00c2\u00a0 One could just as easily add quick links for each band.\u00c2\u00a0 Using the antenna as a full wave on the 2nd harmonic provides radiation patterns that might be more useful, but either choice provides a method to cover each band.\u00c2\u00a0 The initial lost opportunity cost is the need for the transformer.\u00c2\u00a0 For quick and dirty field construction a simple wire dipole or vertical would still be easiest – but mostly monoband, as fan dipoles can sometimes be difficult to tune.<\/p>\n

Future ideas<\/h5>\n

Thinking about trying a different twist on using the FT-140-43 size cores by pasting three of them together for a transformer, and trying the transformers out with 3:1 turns ratios.\u00c2\u00a0 I have enough of the FT-140 size on hand to do this but used my last two of the FT-240 size.\u00c2\u00a0 My first test antenna seems to be a success, so it just need to be put on the air some to get an idea of how it fits in.\u00c2\u00a0 It is always good to have the option available.<\/p>\n

20m\/30m Constructed and Trimmed<\/h5>\n

Using the transformer built from a pair of ft-140-43 toroids sandwiched together, an antenna for 20m\/10m is now built.\u00c2\u00a0 It includes a simple wire tail that can be attached as a link to extend for use on 30m\/15m.\u00c2\u00a0 It should be a simple matter to prepare a wire for adding 40m use.\u00c2\u00a0 With the 40m wire 15m should be use-able with two configurations, either 30m or 40m.\u00c2\u00a0 If 15m is open that might add some interesting changes in radiation pattern when switching from a full wave to a 3\/2 wave.\u00c2\u00a0 May as well add a jumper for 17m too(later-much later).\u00c2\u00a0<\/p>\n

TAP Cheat Sheet, 30m\/20m\/15m\/10m<\/h5>\n

Taps 20m\/30m linked EFHW (jumper to attach 30m\/15m)
<\/strong><\/p>\n\n\n\n\n\n\n\n\n\n\n\n
BAND<\/td>\nTAP<\/td>\nBest SWR<\/td>\n\u00c2\u00a0SWR range to expect<\/td>\n<\/tr>\n
30m(j)<\/td>\n8.5:1<\/td>\n10.25(1.6:1)<\/td>\nEntire band, 1.6:1 with wire drooping<\/td>\n<\/tr>\n
30m(j)<\/td>\n8.5:1<\/td>\n10.1(1.3)<\/td>\nEntire band, 1.3:1 with wire pulled taut<\/td>\n<\/tr>\n
30m(j)<\/td>\n7.5:1<\/td>\n10.3(1.4)<\/td>\nAlternate tap,1.4:1 with wire pulled taut<\/td>\n<\/tr>\n
20m<\/td>\n8.5:1<\/td>\n14.025(1.4)<\/td>\nEntire band favoring CW section<\/td>\n<\/tr>\n
15m(j)<\/td>\n4.5:1<\/td>\n21.010(1.4)<\/td>\nEntire band under 2:1(wire drooping)<\/td>\n<\/tr>\n
15m(j)<\/td>\n4.5:1<\/td>\n21.010(1.0)<\/td>\nEntire band flat with wire pulled taut<\/td>\n<\/tr>\n
10m<\/td>\n6.5:1<\/td>\n28.000-29.25<\/td>\n28.00 thru 28.800 under 2:1(swr 1.2:1 on CW)<\/td>\n<\/tr>\n
10m<\/td>\n8.5:1<\/td>\n28.00(1.4)<\/td>\n28.00 thru 28.75 < 2:1(swr 1.4:1 on CW)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

*(j)= jumper attached for 30m\/15m<\/p>\n

Other ideas and observations<\/h5>\n

LINKING –<\/strong><\/em> Thinking about creating a “linked EFHW” out of curiosity.\u00c2\u00a0 If 10m were reliably open I would pursue the idea seriously.\u00c2\u00a0 The different patterns of radiation going from 1\/2, fullwave, 3\/2, 2xfullwave would be fun to work through.<\/p>\n

Using taps on the transformer <\/strong><\/em>—-After testing with two different tapped transformers, using the taps makes it simple to obtain a good match.\u00c2\u00a0 More on the air testing is needed, but at this point trying to obtain good matches using a single transformer ratio seems futile.<\/p>\n

Different cores = different wire\u00c2\u00a0 <\/strong><\/em>With both transformers I found that the length of wire needed was unique to each configuration.\u00c2\u00a0 The lesson is to build the transformer and tune the wire to the actual transformer being used.\u00c2\u00a0 The ft-240-43 transformer pair would not match the wire cut for the ft-140-43 transformer pair.\u00c2\u00a0 Need to build more transformers to see if a pair of identically built transformers(size and number) will both match the same wire.\u00c2\u00a0 Best guess is that will work.\u00c2\u00a0 But don’t expect transformers with different toroid sizes, or different number of toroids sandwiched together to all work with a set size of wire.\u00c2\u00a0 Be prepared to test or trim.<\/p>\n

Wire droop not ideal<\/strong><\/em> \u00c2\u00a0 Pulling the wire as taut as possible not only shifted resonance slightly, but improved the SWR match on every band.<\/p>\n

\u00c2\u00a0<\/p>\n

\u00c2\u00a0<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

EFHW Experiment Part 1EFHW Experiment Part 2 EFHW Experiment Part 3 UPDATED 2021-04-08Transformers??? <\/p>\n

On a whim I decided to wind a transformer using two FT-140-43 cores.\u00c2 I went with the same 2:1 ratio as the first transformer.\u00c2 SWR testing using this second version showed that all transformers are not equal.\u00c2 The SWR readings taken using the new transformer with the antenna wire as it was trimmed with the larger transformer did not have similar results.\u00c2 It turns out the new transformer would require re-trimming the wire lengths to bring the 40m band into the same SWR curve.\u00c2 Since I had the 80m coil&tail attached using .250 quick connects, it was easy to add wire.\u00c2 Doing that allowed bringing 15m and 10m to good matches.\u00c2 20m also found a sweet spot but only on the 6.5:1 tap.<\/p>\n

New Version? <\/p>\n

Without re-tuning the wire no good matches were obtainable on 40m.\u00c2 Instead of making any permanent changes to the working 40m loaded antenna\/transformer combo I am making a different wire based on a 30m wire length.\u00c2 It will include a quick connect to allow the antenna to cover 20m by detaching the section of wire beyond the ~34 foot 20m wire length.\u00c2 That will provide an antenna capable of 30m\/20m\/15m\/10m.\u00c2 This may become a simple way to add a permanent 30m antenna in the w4kaz antenna farm.\u00c2 <\/p>\n

Maybe I get ambitious and add a second link to include 17m, just for grins.\u00c2 Does an easy tune 30m\/20m\/17m\/15m\/10m antenna sound good?\u00c2 […]<\/p>\n

Continue reading End Fed Half Wave Experiment – Part 4<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[7,13],"tags":[],"_links":{"self":[{"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts\/3444"}],"collection":[{"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3444"}],"version-history":[{"count":16,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts\/3444\/revisions"}],"predecessor-version":[{"id":3483,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts\/3444\/revisions\/3483"}],"wp:attachment":[{"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3444"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3444"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3444"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}