{"id":3387,"date":"2021-03-17T08:22:00","date_gmt":"2021-03-17T12:22:00","guid":{"rendered":"http:\/\/w4kaz.com\/qth\/?p=3387"},"modified":"2021-05-06T22:33:20","modified_gmt":"2021-05-07T02:33:20","slug":"end-fed-half-wave-experiment-part-3","status":"publish","type":"post","link":"http:\/\/w4kaz.com\/qth\/?p=3387","title":{"rendered":"End Fed Half Wave Experiment – Part 3"},"content":{"rendered":"\n
\u00c2\u00a0End Fed Half Wave Experiment – Part 1<\/a>,\u00c2\u00a0 End Fed Half Wave Experiment – Part 2\u00c2\u00a0<\/a><\/h5>\n
The “Tune-up-ening”<\/h5>\n

The first attempts to tune up the real antenna did not go well.\u00c2\u00a0 I found from the trap dipole project attaching the wires beyond the trap was needed to get the higher bands tuned properly.\u00c2\u00a0 This worked against me here.\u00c2\u00a0 With the high impedance on the end fed I was better off tuning the 40m antenna segment without the coil and 80m tail attached.\u00c2\u00a0 Unfortunately, I wasted a lot of time experimenting\/snipping before I decided to detach the inner antenna from the coil.<\/p>\n

Once taking that step, I found I had probably trimmed too much off.\u00c2\u00a0 Tuning for 40m without the coil proved simple enough.\u00c2\u00a0 After that the other bands were easier too.\u00c2\u00a0 I was also able to re-attach the coil and 80m tail, and find tap settings and tail lengths to allow operation with good matches on 80m and 20m.\u00c2\u00a0 With the 20m tails attached 40m operation on the upper edge is possible.\u00c2\u00a0 With tails 40m SWR was a bit high on CW segment, although possible with a tuner.\u00c2\u00a0 10m seemed unaffected by the coil and tail.\u00c2\u00a0 15m provided low SWR only with the coil and tail detached, but SWR of 2:1 up to 3:1 with 80m coil and tail.<\/p>\n

Antenna Stuff<\/h5>\n

The coil as wound measured out to 77.5uh, resonant at 3.85Mhz with 22pf of capacitance.\u00c2\u00a0 It is ~63 close-wound turns on a mystery plastic coil form of ~2 inch diameter, wound with 16ga solid insulated wire.\u00c2\u00a0 The final wire length in the 40m section is xxft(zz.zm).\u00c2\u00a0 The 80m tail is xxft(zz.zzm) in length and the portion for ssb(75m) is xxft(zz.zm).\u00c2\u00a0 To make the choices more flexible for POTA or other portable uses, I have a series of jumpers in several key places.<\/p>\n

The first of the jumpers is installed near the feed point.\u00c2\u00a0 The antenna was trimmed at the feed point for ease-of-access reasons.\u00c2\u00a0 Since I ultimately decided I had over-trimmed before detaching the 80m coil&tail, it seemed easier to insert a jumper there.\u00c2\u00a0 This will also allow\u00c2\u00a0 having an easy method of re-tuning on the fly if it seems necessary in different deployment configurations.\u00c2\u00a0<\/p>\n

The next set of jumpers comes at the junction between the 40m antenna and the 80m coil&tail.\u00c2\u00a0 There are two more jumpers on the 80m tail itself, positioned to allow choosing between a mid-band SSB section centered at around 3.8Mhz or a CW section centered at about 3.575Mhz.\u00c2\u00a0 The lower section will allow use on both CW and in the lower 3.600Mhz SSB segment.<\/p>\n

The antenna can be deployed with or without the 80m coil&tail.\u00c2\u00a0 I found that the matches in the 40m and higher segments are much with the tail removed\/detached.\u00c2\u00a0<\/p>\n

All Taps NOT Ideal<\/h5>\n

As described in previous posts, the transformer brewed up for this project has multiple taps, not the fashionable 49:1 single solution.\u00c2\u00a0 It turned out having the choices of taps gave better SWR matches than any single tap.\u00c2\u00a0 In fact, only one of the taps worked well for the 15m\/10m bands, the lowest impedance 4.5:1 tap.\u00c2\u00a0 For 40m and 80m, the 8.5:1 tap proved the best choice.\u00c2\u00a0 20m SWR curves favored the 7.5:1 tap, although the 6.5:1 tap proved useful with the 80m cw configuration.\u00c2\u00a0 When configured for 80m CW the 6.5:1 tap provides better than a 1.5:1 SWR across all of 20m.\u00c2\u00a0\u00c2\u00a0<\/p>\n

TAP Cheat Sheet<\/h5>\n

Taps 40m and up, bare wire,\u00c2\u00a0 NO 80m coil&tail<\/strong><\/p>\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
40m<\/td>\n8.5:1<\/td>\n7.15Mhz@ 1.2:1swr<\/td>\nEntire band, 1.8:1 up to 2:1\u00c2\u00a0 centered on 7.15<\/td>\n<\/tr>\n
20m_1<\/td>\n7.5:1<\/td>\n14.15<\/td>\nEntire band good favoring CW section<\/td>\n<\/tr>\n
20m_2<\/td>\n6.5:1<\/td>\n14.275<\/td>\nEntire band good favoring SSB section<\/td>\n<\/tr>\n
15m<\/td>\n4.5:1<\/td>\n21.3<\/td>\nEntire band under 2:1<\/td>\n<\/tr>\n
10m<\/td>\n4.5:1<\/td>\n28.2<\/td>\n28.00 thru 28.800 under 2:1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Taps with 80m SSB section
<\/strong><\/p>\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
80m<\/td>\n8.5:1<\/td>\n3.825Mhz@ 1.2:1swr<\/td>\n3.7 thru 3.9Mhz , ?tuner at edges?<\/td>\n<\/tr>\n
40m<\/td>\n8.5:1<\/td>\n7.3Mhz, 2:1<\/td>\n7.2 to 7.3Mhz, tuner needed<\/td>\n<\/tr>\n
20m_1<\/td>\n7.5:1<\/td>\n14.1<\/td>\n14 to 14.35 under 2:1<\/td>\n<\/tr>\n
20m_2<\/td>\n6.5:1<\/td>\n14.225<\/td>\nBest choice, entire band good favoring SSB section<\/td>\n<\/tr>\n
15m<\/td>\n4.5:1<\/td>\n21.05 @ 2:1<\/td>\n21.0 to 21.35, SWR over 3:1 above 21.35<\/td>\n<\/tr>\n
10m<\/td>\n4.5:1<\/td>\n28.2<\/td>\n28.00 thru 28.800 under 2:1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Taps with 80m CW section
<\/strong><\/p>\n\n\n\n\n\n\n\n\n\n\n
BAND<\/td>\nTAP<\/td>\nBest SWR<\/td>\nSWR Range to expect<\/td>\n<\/tr>\n
80m<\/td>\n8.5:1<\/td>\n\u00c2\u00a0<\/td>\n3.525 to 3.75 <2:1<\/td>\n<\/tr>\n
40m<\/td>\n8.5:1<\/td>\n\u00c2\u00a0<\/td>\n7.2 up under 2:1<\/td>\n<\/tr>\n
40m_2<\/td>\n8.5:1<\/td>\n1.3:1@7.3<\/td>\n40m jumper ins, useable on cw<\/td>\n<\/tr>\n
20m<\/td>\n7.5:1<\/td>\n14.0<\/td>\n14 up to 14.275 < 2:1<\/td>\n<\/tr>\n
20m_2<\/td>\n6.5:1<\/td>\n1.5<\/td>\n40m jumper ins, all band<\/td>\n<\/tr>\n
15m<\/td>\n4.5:1<\/td>\n21.245 @ 2:1<\/td>\n\u00c2\u00a0<\/td>\n<\/tr>\n
10m<\/td>\n4.5:1<\/td>\n28.1<\/td>\n28.0 to 28.7 < 2:1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u00c2\u00a0Test Deploy
<\/strong><\/p>\n

All tuning was done with the antenna strung up using two Jackite telescoping poles as supports.\u00c2\u00a0 A 31 footer is used for the vertical portion, and the feed point is at about 4 feet off the ground.\u00c2\u00a0 The horizontal runs out about 40 feet to the second mast, a 28 footer.\u00c2\u00a0 The second mast supports the weight of the wire and the loading coil, probably the heaviest portion of the antenna if used.\u00c2\u00a0\u00c2\u00a0 I ran a 7 foot long counterpoise wire, and a six foot long coax jumper angles down to ground level from the feedpoint to the first choke, eight turns of coax wound on a ft-240-31 ferrite(another 6 foot jumper for that).\u00c2\u00a0<\/p>\n

The short section of straight coax jumper will likely be a second counterpoise for the antenna.\u00c2\u00a0 The first choke plugs into a second choke constructed of 10 turns of a 14ga wire pair wound on a second ft-240-31 ferrite and mounted in an enclosure.\u00c2\u00a0 From the chokes a fifty foot long lmr 240 feedline is attached, and all testing was done at the end of the feedline.\u00c2\u00a0 That simulates the most likely portable deployment.<\/p>\n

FWIW, SWR results did not change when the fifty foot section of coax was removed.\u00c2\u00a0 Will be a curiosity to find out if altering the shape of the deployed antenna changes SWR.\u00c2\u00a0<\/p>\n

Additionally, I toyed around with inserting pieces of wire as jumpers to lengthen the 40m section.\u00c2\u00a0 These jumpers are inserted close to the feedpoint on the vertical section.\u00c2\u00a0 I inserted them to try to improve 40m SWR when the 80m loading coil&tail were linked in, as 40m SWR was too high for CW operation without tuner with tail attached.\u00c2\u00a0 This turns out to be a useful compromise solution.\u00c2\u00a0 It will allow using either 40m or 80m without adjustment, and 20m\/10m can be used with tap change.\u00c2\u00a0 15m is the odd man out in this configuration, but could maybe be used with a tuner.<\/p>\n

Stress Test Awaiting<\/strong><\/p>\n

Following are some key down stress tests to gauge how well the RBN can hear and to see if there will be any heating in the ferrite cores when at 100w levels.\u00c2\u00a0 Perhaps a POTA operation would be better.\u00c2\u00a0\u00c2\u00a0 No “SWR creep” was found when I did 60 second key down tests on the dead bands at 1800Z.\u00c2\u00a0 Both extreme ends were tested at 60 second key down, 80m and 10m.\u00c2\u00a0 Then a series of test transmissions that consisted of three repetitions of the test string: “V V V TEST W4KAZ W4KAZ W4KAZ V V V”.\u00c2\u00a0<\/p>\n

\"RBN<\/a>

RBN Spots from 40m EFHW at 1800Z on 2021-03-11<\/p><\/div>\n

The RBN spots from 1800Z show decent results, not too dissimilar from what I am accustomed to seeing from the permanent wire dipole antennas.\u00c2\u00a0 The test antenna is deployed in a much-less-than-ideal location.\u00c2\u00a0 The test EFHW horizontal section is running parallel to the horizontal tail of my permanent 160m inverted L, and it is only about 20 feet away.\u00c2\u00a0 So I’m not too concerned with the locations of spotting stations.\u00c2\u00a0 I expect to try a POTA activation soon, which will maybe be more interesting.<\/p>\n

\"RBN<\/a>

RBN Spots from 40m EFHW at 2345Z on 2021-03-11\u00c2\u00a0<\/p><\/div>\n

Likewise the above set of RBN tests run later, near to and just after local sunset\u00c2\u00a0 @2330Z, show fairly typical results.\u00c2\u00a0<\/p>\n

\"80m<\/a>

RBN Spots from 40m EFHW at 2345Z on 2021-03-11\u00c2\u00a0\u00c2\u00a0 *<\/p><\/div>\n

I expected 80m results to be poor but they were maybe better than my low expectations.\u00c2\u00a0 Nothing great, but certainly good enough for an easy to deploy portable antenna.\u00c2\u00a0 Better to have some 80m capability than zero capability.\u00c2\u00a0<\/p>\n

Next Question:\u00c2\u00a0 What happens if I use a different transformer?<\/h5>\n

see part4\u00c2\u00a0\u00c2\u00a0 EFHW Experiment – Part 4<\/a><\/p>\n

*<\/p>\n","protected":false},"excerpt":{"rendered":"

\u00c2 End Fed Half Wave Experiment – Part 1,\u00c2 End Fed Half Wave Experiment – Part 2\u00c2 The “Tune-up-ening” <\/p>\n

The first attempts to tune up the real antenna did not go well.\u00c2 I found from the trap dipole project attaching the wires beyond the trap was needed to get the higher bands tuned properly.\u00c2 This worked against me here.\u00c2 With the high impedance on the end fed I was better off tuning the 40m antenna segment without the coil and 80m tail attached.\u00c2 Unfortunately, I wasted a lot of time experimenting\/snipping before I decided to detach the inner antenna from the coil.<\/p>\n

Once taking that step, I found I had probably trimmed too much off.\u00c2 Tuning for 40m without the coil proved simple enough.\u00c2 After that the other bands were easier too.\u00c2 I was also able to re-attach the coil and 80m tail, and find tap settings and tail lengths to allow operation with good matches on 80m and 20m.\u00c2 With the 20m tails attached 40m operation on the upper edge is possible.\u00c2 With tails 40m SWR was a bit high on CW segment, although possible with a tuner.\u00c2 10m seemed unaffected by the coil and tail.\u00c2 15m provided low SWR only with the coil and tail detached, but SWR of 2:1 up to 3:1 with 80m coil and tail.<\/p>\n

Antenna Stuff <\/p>\n

The coil as wound measured out to 77.5uh, resonant at 3.85Mhz with 22pf of capacitance.\u00c2 It is ~63 close-wound turns on a mystery plastic coil form of […]<\/p>\n

Continue reading End Fed Half Wave Experiment – Part 3<\/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\/3387"}],"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=3387"}],"version-history":[{"count":28,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts\/3387\/revisions"}],"predecessor-version":[{"id":3449,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=\/wp\/v2\/posts\/3387\/revisions\/3449"}],"wp:attachment":[{"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3387"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3387"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/w4kaz.com\/qth\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3387"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}