Compromise: Good performing antennas that don’t require two 65′ masts.
- High Bands (17, 15, 10,6) – sloper
- Low Bands (80, 160) – top hat loaded 43 foot vertical
- Forty meters – Vertical yagi
High Bands: A 23′ dipole sloper models well with EZNEC on all the high bands including 6 meters. One end can be attached to the apex of the 60 foot 20 meter tower and sloped down at 45 degrees. Ladder line can be sloped away at a right angle from the center feed point. Modelling shows considerable gain on each band at low take off angles and impedances easily matched by a tuner.
Low Bands: Modelling shows that adding top hat capitance can improve performance of a 43 foot vertical on 80 and 160. The object is to add enough top hat to drop the resonance to half way between 80 meters and 160 meters, which is 2.3 MHz. Impedances are hard to match for a tuner but a relay controlled matching circuit should be easy to build.
Forty meters: Following a QST article from July, 1972, The W2FMI 20-Meter Vertical Beam, we scaled to 40 meters. This is a three element yagi made of three quarter-wave verticals. Gain is less than a dipole but better than a single vertical. It will be aimed toward Europe.
Two Additional Enhancements
Receive Loop: Perhaps a DX Engineering RF-PRO-1B Active Magnetic Loop Antenna will improve reception. It covers all HF bands and could make up for some loss by improving signal-to-noise ratio.
Six meter halo: Might give us improved 6 meter performance. It is omni directional, has some gain, and comes highly recommended (QST, March, 2018). It will be mounted at the height that EZNEC models best, 22 feet.
Both the north and the south 65′ aluminum masts went down in the snow storm Sunday. They both failed in almost the same place about two-thirds up. What a mess. First the south mast, then the north.
Plans for what to do next are not worked out. KC0RF has made several suggestions: slopers from the tower, a 43 foot vertical, a HyGain Hytower, and replacing the masts with 65′ Telrex tubular crankup masts. We’ll use EZNEC to help us evaluate these suggestions and maybe come up with some of our own. One of my ideas would be to replace the .058 tubing with .12 inch.
A Plan Emerges Finally
Consider this: they both failed at about the two thirds point and the highest level of guys had been moved up to the top of the mast against the DX Engineering instructions. The top would not have been supported per the instructions and surely would have failed with antenna ropes pulling horizontally. That’s why the guys were moved up. Unfortunately it left too large a section unguyed. Armed with this analysis the next attempt will be to guy exactly per the instructions and then add a fifth set of guy ropes to the very top. Replacements for the bent sections will be ordered. Only one mast will be done this way as a test.
January 27, we salvaged the north mast and re-purposed the tubing that wasn’t damaged. Taking one of John’s suggestions we made it into a 43 foot vertical. The North mast now:
So far performance has been excellent, working quite a bit of dx. Next upgrade will have to be a higher power tuner (MFJ 998RT) so we can run a few more watts to make up for the inefficiencies. Frankly, I’m surprised at how well this antenna performs.
South mast: A week later we cut off the bent top sections. South mast now:
A road grader in the background is building an access road in the easement next to our property. Progress I’d be happy to forego.
Unfortunately with John’s help we tried to raise the repaired 65 foot south mast complete with 5 guy levels and it collapsed when it was about 90 per cent up. This makes the fourth time one of these aluminum masts has collapsed. You know what they say. Four strikes and you’re out. No more 65′ masts at W0QL. Next we’ll look for some suitable solutions closer to the ground.
The main 56 foot low band vertical has been extended to 65 feet. It took a full day to do it because of it’s unwieldiness and a constant 16 mph wind. Thanks to John, KC0RF for giving up a full day to help. Here’s what it looks like with the additional height and a small top hat to resonate to 3.573 kHz (the FT-8 freq). This is both a vertical antenna and the north mast which is planned to hold up two dipoles. The south mast (below) is planned to have the other end of one of the dipoles attached.
The 30″ top hat is very hard to see when it’s 65 feet up in air. A better picture is coming soon.
The antenna is designed as a full quarter wave on 80 meters. Using a MFJ 259B the impedance at 3.573 kHz reads 55 -j0. SWR is 1.1. Apparently we hit the resonance perfectly but the ground screen needs to be improved to bring the resistance down to 36 ohms. The match was planned to be a direct match for a 50 ohm coax. As an experiment we left the existing tuner installed and tried it on other bands. It works on all bands, 160 through 10 meters even though the take off angles may be awful and the tuner losses may be especially high at the even harmonic frequencies. We’ll leave the tuner in for a a few weeks to see where it works and where it doesn’t.
Once in a while a little extra help is needed to obtain a contact with a DX station. That extra help can come in the form of a few more watts. When a difficult DX contact is completed we call that being deserving, as in, “We are among the deserving” (Where Do We Go Next, Martti Laine, OH2BH). Here is a photo of the new amp and my silly grin shows a combination of emotions. Sheepish for adding power to a weak signal mode but thrilled at the same time.
(Actually the emotion is more, “Can I get this damn cell phone to take a selfie”.)
Design contraints of a remote base off grid quickly narrow down the choices of linear amplifiers. The SGC SG-500 was the obvious choice because it changes bands automatically using rf sensing, runs the finals at 12 volts, and has a remote on/off switch ability. Luck was with us when we found this pristine SG-500 at a good price online at QRZ Swapmeet.
The amp can draw up to 90 amps. We rearranged the battery banks to dedicate one bank to the amp. Everything else is on the other bank. Testing showed up no problems except a tired SO239 coax connector. We escaped replacing that by using a PL259 with a slightly longer center pin so it would push against the solder cup at the back. Deferred maintainance. With 10 watts input the output is 150 watts with no complaints from anything else in the station. On to the first on-air test.
Wow, amazing, superlatives are not enough. Noticing a big pileup for a station with the call 3D0AY (Swaziland) I found a clear frequency and clicked the transmit button. Seven others were calling at the same time. With only four calls, on the 4th transmission he came back to me! Here is the proof.
As soon as Swaziland anwered my call another station jumped on our frequency. I found another clear spot and tried to complete the qso with Swaziland. He came back again and we completed the contact. Another station immediately jumped on the new frequency. A difficult qso but my station joined the “deserving”, thanks to the new amp. I’m hooked. I’ll be using this whenever a pileup is tough.
Unfortunately there has been no second qso using the amp. It seems to be malfunctioning. It began immediately switching off and the high vswr warning light came on. Changing to manual PTT got rid of the vswr alarm but no rf comes out of the amp. It draws a large amount of current but where are those amps going? It will probably have to go back to SGC for a look. For the time being we are not using an amplifier.
Update: I tried the amp using a different radio and it works perfectly.
Sixty-five foot mast from DXEngineering completed today and looks amazingly vertical. Getting it up was like raising a wet noodle. Here’s what it looks like on the ground.
The secret is to never let the attachment point get below the bow point. Lift the upper sections first and keep them under upward pressure so a downward facing bow never forms.
When it’s all over it looks like the top picture. This will be the south support for a 40 meter dipole and possible for a 630 meter antenna.
Adding a tuner to the 20 meter yagi didn’t work out so well for 15 meters and 17 meters. Next trial is erecting end fed half wave verticals for those two bands today. We are using LNR PAR EF-17 and EF-15 antennas mounted on two fiberglass poles. Below is the 17 meter version.
Preliminary testing has been successful when compared with the yagi/tuner combination. We attempted to answer cq’s from Japan with the yagi on 17 meters to no avail. Switching to the end fed half wave produced an immediate qso with JN8QNF.
By adding a tuner to the 20 meter antenna system it is now possible to operate on 15 meters, 17 meters, and 30 meters in addition to 20 meters. The 20 meter yagi acts like a dipole on the new bands. No gain or much directivity but a dipole at 60 feet is a big improvement over the verticals that have been in use. The tuner is a LDG Electronics model RT-100 remote automatic tuner mounted in the shack. This is similiar to using the tuner in a transceiver except this has wider coverage. A conjugate match can be made anywhere along a transmission line. However, any time a tuner is located at other than the antenna feed point there is loss introduced in the form of coax loss due to swr and cable loss. This is an experiment to see how well the concept will actually work in practice.
Our installation consists of 160 feet of LMR 400 coax between the transmitter and the antenna feed point (100′ to the base of the tower and 60′ up the tower). If the tuner was moved to the base of the tower 100 feet of coax would be bypassed. For these calculations we use the KV5R.com web site. At 17 meters for example, total loss at 160 feet is 2.8dB (coax loss plus swr loss). For 25 watts out from the transmitter the antenna would receive 13 watts. Moving the tuner to the base of the tower would improve the loss to 1.2dB. The antenna would receive 19 watts. We ignored the loss in the 100 feet of coax from the transmitter to the tuner. That loss would be .5dB (or 3 watts in this example) with virtually no swr loss. Therefore the coax would deliver 22 watts to the input of the tuner and the antenna would receive 3 watts less.. With 1.2dB of loss the antenna was receiving 19 watts. Now it would receive 16 watts. In conclusion if we moved the tuner to the base of the tower the antenna would receive 3 watts more power or .5 dB (16 watts vs 13 watts). Is it worth moving the tuner to gain 3 watts (or .5 db)?
SWR Loss at 18.100 MHz
100′ LMR400 = 3 watts
Update: It seems to work on 17 meters. FT8 contacts with Europe have been made. For the next experiment it would be fun to try a better tuner, such as the MFJ 998RT, at the base of the tower. This tuner would have less loss plus allowing bypass mode and tuning a wider range. It is expensive and putting a up a second antenna might be less money.