Adding A Tuner To 20 Meter Yagi.

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.

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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.

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630 Meters

630 meters (and it’s partner, 2200 meters) were given official permission to operate as of October 16, 2017.  I hope to operate 630 meters with JT9 and WSPR (and maybe even FT8).  A process to register a station has been implemented to notify power companies of amateur operation.  Of course, W0QL filed an application immediately and if not denied will be authorized to operate beginning October 17, 2017 (one day later).  The FCC notice started off a long list of action items to get done before we can get on the air.  We made some quick decisions.

  • Antenna:  The existing 6 meter antenna is mounted on a 39 foot aluminum mast.  That mast will be pressed into service right where it is as the vertical portion of an inverted L antenna.  The plan is to lay radials around the base of the vertical after cutting the weeds to make room.  A thin wire will run from the top of the mast over to the top of the 20 meter tower about 200 feet away.  Plans came from this article: http://www.wd8das.net/630mPractical.pdf
  • A variometer will be built to resonate and match.  The variometer is under construction using scrap pvc pipe.  Plans for the variometer came from http://www.g0mrf.com/variometer.htm.

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  • Rig:  Luckily the existing Kenwood TS-480 receives down to the operating frequency for 630 meters, 474 kHz.  Antenna port 2 can be used leaving antenna port 1 in tact for the existing station.  A 630 meter downconverter has been built that provides 20 watts output from 1 watt input.  The TS-480 minimum power output is 5 watts so we will need an attenuator in the line when transmitting.  With a relay driven by the PTT line the attenuator can be bypassed for receiving.  Also under consideration is the K3 because it can put out 1 watt and wouldn’t need an attenuator.

U.S. Amateurs will be allowed to run a maximum of 5 watts EIRP, which is about 1.6 watts ERP.  The short antenna will be inefficient relative to a full size dipole (991 feet long) and should keep us legal.  Radiation resistance is estimated to be .4 ohms and ground loss 6 ohms.  That gives us efficiency of 6.25 per cent.  Our 20 watt downconverter would radiate 1.375 watts erp and be compliant with the regulations.

The magnet wire arrived in the mail today.  This will become the winding for the variometer —  325 feet of 16 awg.

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The coils are wound:

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UNfortunately, the coil only measures 800 micro henries and we need 1900 according to the online calculator.  The eBay listing said the diameter of the wire is 0.0520″.  Two hundred turns would be about 10.4″.  Something is not correct (could this actually be the radius instead of the diameter?). Back to the drawing board.  Could wind remaining wire on a second piece of sewer pipe as one option. Or start over and make the splices a tap point. Alternatively I might try it temporarily on the big vertical in Strasburg.

 

Google Maps aerial picture

Google Maps (maps.google.com)  now has an updated aerial picture showing the Strasburg remote base.  We’re official at last!   Prominent in the picture is the shed and the solar panels.  Faintly visible are the radials and the coax running to the vertical antenna.  The tower was not up yet but the partially dug hole is visible.

cropped aerial

5 Loose Ends Tied Up

  1. Is the beam pointing in the direction the rotor says it is?    It was within 5 degrees which is good enough considering the antenna has a 30 degree beamwidth.
  2.  Replace faulty power unit.  Bit the bullet and bought a new Rig Runner 4005i to replace the one that had been damaged by a lightning surge in the summer.  Moved the damaged one down the line to the radio and some peripherals. It still turns the power on and off; it just can’t read the voltage or current since the lightning surge.
  3. The Internet controlled interface to the solar controller can be reset over the Internet now.  The Morningstar Sunsaver Duo and it’s remote, the EMC-1 sometimes locked up and couldn’t be read over the Internet.  Installed are relays on the EMC-1 wiring to allow it to be reset remotely.
  4. Braided straps on the big vertical antenna should improve the rf path through the tuner to the ground radials.  These straps replace the single 12 gauge wire we had been using.  The tips of the straps are soldered to keep water from seeping into the connection.

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5.   Waterproof the tower legs sticking down into the concrete.  Water in the legs from the summer rains was pumped out and expanding foam was squirted in. Water does not drain out the bottom like one would expect.  On the last tower it took 10 years but the steel legs finally rusted through and had to be replaced.  Hopefully this problem has been eliminated with the expanding foam sealant.

More loose ends:  put up a sign on the east side targeting the easement, “Danger, 13,400 Volts”.  Will that make some people keep their distance?  Maybe.

checked and topped off battery fluid, labeled all equipment with i.p. Address and port number.

Solar Panel Addition

Today we added a fourth solar panel for the purpose of improving early morning power output.

IMG_0205The other three panels are aiming due south tilted at 48 degrees for maximum December 22 output at noon.  This new panel is aimed due east for the first sun of the morning tilted to obtain peak output at 8 am.  We often want to operate just after dawn when the batteries are at their lowest.  This panel should fill in the gap until the main panels are getting sun.  We still need to connect the wires.

WSPR Station

A Weak Signal Progagation Report (WSPR) station is on the air now from the permanent site at Strasburg.  It runs 1 watt on multiple bands.  WSPRnet.org shows the results.   Hardware is a Yaesu FT-817 transceiver and an Intel Compute Stick computer.  Software is WSJT-X Ver 1.8 running in WSPR mode.  Antenna is a Hustler 6BTV trap vertical.  Ground radials are welded-wire fencing.

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KC0RF, John, and I were just finishing up when rain hit.

Control is done over the Internet using a remote access application, Teamviewer.  FCC regulations specify a beacon can only run when an operator is present to control it.  Whenever I leave the house the WSPR station is shut down by using Teamviewer.

Here’s a random screen snap of the WSPRnet.org results for the last hour.  These stations have “spotted” my 1 watt beacon and posted it to WSPRnet.org in the last hour.  We’re getting many more spots with the base antenna out here than we did with the mobile antenna at home.

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August 15, 2017 – measuring the swr with a MFJ-259B antenna analyzer showed high swr on 30 meters and 80 meters.  We changed the WSPR configuration to only listen on those two bands.  Hopefully we’ll get time to readjust the 6BTV before the eclipse next Monday.

It’s working now but a few hurdles had to be cleared to get this station on the air, as you’ll see in the previous WSPR post.

WSPR Station

The Solar Eclipse QSO Party urges, “Operate a wide-band automated receiver at your station” like a wspr station.  The station has been in staging at home before it gets deployed to the permanent site in Strasburg but not working correctly.  Finally a breakthrough.   Today we figured out a problem.  Now we’re seeing our wspr station being spotted on wsprnet.org, running only 1 watt and feeding a Hustler mobile whip antenna.

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This is the Hustler mobile antenna getting that big 1 watt signal around the country.

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The WSPR station being staged before deployment looks like this.

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The computer is an Intel Compute Stick, on the left side half way up running Windows 10 and WSJT-X version 1.8.  The red box is a West Mountain Radio PlugNPlay Rig Runner to interface to the Yaesu FT-817.  The yellow candy wrapper is shrink wrap around a dc-to-dc converter.  It takes in 12 volts dc and converts it to 5 v dc for the powered usb hub and for the Intel Compute Stick.  Green and blue plugs from the PlugNPlay go into an external usb sound card.  One of the usb dongles is a Yaesu CT-62 CAT interface cable.

Deployment plans include packaging the above apparatus into a fiberglass outdoor enclosure, then adding a solar panel, controller, and batteries.  The permanent antenna will be a Cushcraft AP8A trap vertical picked up at a recent hamfest.  The complete 12 volt station draws 1.3 amps when transmitting (at 1 watt) and draws .6 amps when receiving, including the computer. Can’t use an automatic tuner because wspr changes bands and listens before transmitting.  That means the tuner is still tuned to the previous band instead of the current one.  Must use resonant antennas like trapped vertical.

We’ll turn on band hopping and cover 80 through 10 meter bands.  If we get the ambition we’ll add a 6m vertical stub and cover that band, too.  This project is targeting the August 21, 2017 solar eclipse.  In addition to WSPR we plan to operate the Solar Eclipse QSO Party using weak signal modes JT65, JT9, and FT8 on the main station. We’ll be receiving on 630 meters and transceiving on 160 through 6 meters making as many QSO’s as we can.

First plan went out the window because a trapped vertical needs radials and the weeds  make that impossible.  Plan B is to try a Comet CHA250B because it requires no radials.  It just didn’t get a signal out. Out the window.  Plan C is to receive only at Strasburg and transmit only from home.  Can’t receive from home due to a high noise level.  But at Strasburg  when unchecking all the transmit boxes in wspr it no longer band hops.  Is this a bug?

A solution popped up while reading the manual to try to see why it stopped bandhopping.  There is a “tune” checkbox that sends unmodulated carrier for a few seconds after changing bands.  We just happen to have the ideal tuner — a SGC SG-211.  We’ll try that next.

The SG-211 failed because it needs more than a watt for tuning.  Next we tried a LDG RT-100 and it worked perfectly.