Category Archives: Antennas

Listening to Ham Satellites

I have long wanted to try the amateur satellites. Back when I was a kid I had my trusty Allied receiver and my AO-7 tracking tool but try as I might I never picked up a signal. Today I loaded up the GoSatWatch app on my iPhone and started looking for passes with the aim to at least pick up a signal. There was a decent pass of AO-92 Fox-1D so I tuned by rig to 145.880 Mhz and turned off the squelch. Sure enough a few minutes after the pass started I began picking up signals from the satellite.  This was using my standard discone base antenna. The signals never got really strong but it was encouraging to know that the timing piece worked out well. You can guess what will be coming next…a handheld dual-band yagi.

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Where have I been?

The life thing has been pretty disctracting from ham radio the past few weeks. I just returned from a week long business trip to the Philippines and then had a bunch of catch up to do. This week I started making Field Day and Portable operation preps. I took out all my battery packs and charged them with the solar panels. All are ready to go now.

I ordered a cool little gizmo for the FT-817ND. It is a 3D printed power connector that fits nicely on the back of the radio and converts the power inputs to Anderson powerpoles. I got mine from Ebay:

s-l500

Regarding Field Day, I am still thinking about a 20m beam.  I’ll be doing some modeling comparing the Buddistick, the 2 element vertical beam and a 2 element, inverted-V wire beam. I have already built two of these three and have good results on QRP.

I tried some operating today but so far conditions have been…well they have been pretty bad. SFI=68 and SSN=0 makes for some pretty bad propagation. Definitely need to up the antenna game.

QRP Tests of the 2el Vertical Beam

Rainy day today.

I had planned to take down the vertical beam antenna today and send up the end fed half wave to test for possible field day use. So instead I have left the 2el vertical beam in place and cranked down the power on the IC-7300 to 5W on SSB. I frankly was not expecting much as band conditions have been awful on 20m. I called CQ for a minute or two and a portable station in North Carolina picked me up. We had a short QSO and I received a 59 signal report. Called CQ again and picked up a station in Georgia. I was having more trouble receiving than he was in hearing me. QSB on 20m is pretty bad sometimes. Made one more call and was picked up by a station in KS who gave me a 57. Made  these three contacts over 10 minutes on 5W.

There is hope for Field Day this Year!

miniVNA and Choke Measurements

I recently bought a miniVNA Pro analyzer:

minivna_pro

This is a pretty cool little device that goes beyond just analyzing antennas. One of the first tasks I set this to was measuring some ferrite chokes for comparison. The miniVNA makes quick work of this in transmission mode and in saving the data in Excel format. Here are choking impedance plots for three ferrite based chokes:

chokes

In blue is 9 turns of RG-8X around two FT240-43 cores. This has the best choking performance. The orange plot is a 1:1 choke balun made from an ebay kit. The grey plot is an MFJ-915 line isolator.

2el Vertical Beam Antenna WSPR Results

I ran the 2el vertical beam antenna on 20m WSPR for most of the last week. This time I looked at the WSPR challenge data as compared to N5CEY’s station about 15 miles away. During the week we both made the WSPR challenge scoreboard. On some days I had a higher unique count while on others N5CEY did. The WSPR Challenge site provides a list of all the stations heard in a 24 hour period along with their counts. This can be downloaded and sorted to see which stations had the highest counts. The data for a specific station can then be downloaded over the time period. Here is the count comparison:

wspr challenge counts

Here is a plot of the reported SNR vs time to K8JBV in Ohio from both my station (red) and N5CEY (blue):

WSPR comp

This chart is fairly typical and shows that N5CEY has about a 6dB higher SNR at his station vs. mine. I did note at least two stations, one in Georgia and the other in Florida, that had SNR roughly equal at the two receiving stations. This correlates well with the direction I have the vertical beam pointed. Likewise stations on the backside of the beam have a  few dB more separation.

I am pretty happy with the performance of the vertical beam antenna overall. What I would like to do next is operate portable from a more rural location and measure and differences in SNR on WSPR.

Field Day and the 2el Vertical Beam

I came across an interesting read from Jim, N2GXJ entitled “Thinking about Field day Antennas“. This talks about Field Day scoring and how to improve your score. He points out that the key to Field Day comes down to the sheer number of QSO’s you make irregardless of where they are from. Jim starts by looking at poulation density from the US Census as an indicator of where ops will be located:

2018-04-10_9-42-47

This map tends to confirm my previous experience that the bulk of contacts are made up and down the east coast and in California. Last year I ended up running at 45W due to poor propagation and did notice many stations coming in from California. I made the mistake of not working more of them.

So from my QTH in South Texas I need to target the East and West coasts with daytime activity on 20m and 15m. The 2el vertical beam for 20m will definitely be a good choice for pointing to the east coast and should let me go back to QRP levels. I’ll try and test this out this coming Saturday if the weather holds (good to test the battery system while I am at it).

The 2el Vertical Beam Lives!

Made a run to Home Depot this morning and bought the PVC bits I needed to build the 2el vertical Beam I described in a previous post. The PVC is for the antenna mount to raise the feed point up to about 8 feet. I had some issues laying the elements out in the backyard as a tree was in the way. The two elements are 16 ft apart which is a bit further than the 13 feet modeling showed was optimum. I started by setting up the driven element. this went together very similar to the homebrew Buddistick with the exception that the fishing pole allows me to go full length. It tuned under 2:1 SWR across the whole 20m band. The reflector was even easier as it does not need to be tuned. I used one continuous piece of wire for the element and radial and keep the distance to the radial end at 14 feet. The beam is pointed in roughly a 45° bearing towards the northeast USA and Europe.

I should mentioned I did all this in a dead calm and in very muggy conditions outside today. I did not like the was the PVC was bending but rather than properly guy them I opted to try the antenna out a bit first…what could go wrong? I ran WSPR for about 2 hours with the following result:

2018-04-07

Note the high density of spots to the NE and the two spots to Europe. Pretty good for this time of day. Some SSB work towards the Mississippi QSO party yielded several “strong signal” QSO’s. I also made a QSO to Spain. After I closed that QSO, I switched to the S9V31 and noted a drop on the S meter from S4 to S1 when he was transmitting. Not sure what to make of that as 3 S units represents an 18dB change in signal strength. Perhaps the difference in pattern?

Did I mention what could go wrong? Let me first mention that PVC is like a wet noodle. The reflector was supported somewhat by some nearby tree branches but the driven element was not cooperating. I leaned a step ladder against it to provide a bit of support. Now remeber I did not guy it down as I was anxious to test it out. The weather shifted while I was gathering data. A cold front blew in and it started to rain lightly and the wind started gusting. The antenna has not failed but I don’t expect it to stay up through the night. The driven element is leaning over quite a bit in the breeze and I expect it to flop over at some point. The good news is this is hard to damage.

I’ll guy it up tomorrow for more extensive use. I think this is finally a winner in the gain department. Setup is fairly easy with the only thing I need to improe being how to get the feed point to 8 feet and still keep it portable.

Next Vertical Beam Experiments

My next experiment with a vertical beam antenna for 20m is coming up this weekend. My plan is to start with essentially a full length “Buddistick” on 20m using a fishing pole. I am going to plant 2 feet of a 5 foot 3/4″ PVC pipe as an initial support. On top of this will be another 5 foot 3/4″ PVC pipe joined with a pipe coupler. On top of this is a 3/4″ pipe coupler plus a 3/4″ to 1/2″ pipe adapter. A 12 inch length of 1/2″ PVC pipe will go on top of that and the telescopic fishing poles will slip on to this. Both the reflector and driven element will be mounted in this way. I may have to guy the mounts but short guys should work.

The driven element will have it’s feed point at 8 feet. The vertical element will be 16.5 feet long. The radial will be 17 feet long and slope down to an electric fence post at 4″ high. The reflector will be 13 feet away and be identical to the driven element except the vertical wire is 17 feet long followed by a 17 ft radial also mounted 4 feet high. Here is some EZNEC plots of this configuration:

2018-04-05_13-44-14

I am expecting that this configuration will be below 2:1 across the whole band, provide good low angle radiation, 3-4 dBi of forward gain and 10dB of Front to back. This should be easy to build and deploy

Measurement and Comparison of Common Mode Chokes

I have several common mode chokes in the shack today that I wanted to measure and compare against each other. This seemed like a good application for the low cost VNA I bought a couple of months ago. The setup is shown on the N4SPP website. Only the shield oif the chokes is connected to the center pin of each VNA input. The sweep is done in Transmission line mode and the result is Transmistion loss and phase. This was run after a calibration sweep using a short. I has some concerns over the overall accuracy but the results relative to each other is a good start for comparisons. The chokes I measure are two ugly baluns:

IMG_1487

12T & 14T of RG-8X on an FT240-43 Toroid:

IMG_1486

A 1:1 balun kit I ordered and made off of Ebay (after being outdoors pretty ugly in its own right):

.IMG_1489

and finally the guts of a MFJ-915 line isolator. I say the guts because the isolator originally was encased in PVC pipe but the connectors were off center and did not allow installation of the mating connector. I cut this off and wrapped the connectors in silicone tape.

IMG_1488

This graph shows the resulting data on sweeps from 3Mhz to 15Mhz:

2018-03-19_15-05-13

Overall, looking for damping in the range of 25-30 dB. At first glance all of these chokes all look about the same with the exception of the MFJ line isolator which although relatively flat has readings over 20 dB. G3TXQ has a great write up on the choking resistance. He notes that an issue with the “ugly” balun is that their impedance is almost entirely reactive with the exception of a small band of frequencies around resonance.

“Reactive chokes have the disadvantage that they can “resonate” with a CM impedance path that is also reactive but of opposite sign – in some cases actually increasing the CM current flow rather than choking it.”

I removed the ugly balun and replaced it with the 14T Toroid Choke at the feedline and added a 12T Toroid choke at the IC-7300 antenna input with a 1 S unit drop in the noise floor noted. I will replaced these with mix 31 toroids of the same size which should give a flatter, broader response below 15 Mhz. I also have a 1:1 balun on order from Balun Designs for use at the feedpoint. I’ll take some measurmeents on these and post and they become available.

Lowering the HF Noise Floor

Previous posts have reported on WSPR performance with my vertical antennas especially compared to data collected by a nearby Ham (Cliff – N5CEY) with a similar antenna setup. The metric is how well a given antenna receives unique spots over a 24 hour period as documented by the WSPR Challenge site. I have always seemed to lag behind Cliff’s receive performance in spots and in DX received. I have asked Cliff about the specifics of his setup and came to the conclusion that he has a significantly lower noise floor at his QTH in the country versus mine in the city. Cliff’s QTH is about 12.5 miles north of mine in a rural area. He is closer to the coast and likely has much better soil conditions as well. His antennas on WSPR are all 1/4 wave verticals on 40m, 30m and 20m. I have an “ugly” balun installed at the feed point of my vertical and about 30 feet of RG-8X to the shack entrance. There are about 8 loops of coax at the shack entrance. Inside the shack are various patch cables connecting switches, antenna tuners, SWR meters and the Timewave ANC-4 to the IC-7300. Lots of nearby noise sources including PC’s, cable modems, wifi routers etc.

So the task before me is how to lower the noise floor at my QTH to bring in weaker signals. I have done quite a bit of research and finally came upon some discussion of the effects of Common Mode currents on noise floor. My next post will detail some measurements on various common mode current chokes but for now suffice it to say that changing my common mode choke arrangement has had a positive effect on the noise floor. Here is what I did:

  1. Added a CMC consisting of 12 turns of RG-8X around a FT240-43 toroid core right at the IC-7300 antenna connection. This resulted in a 1 S (6dB) unit reduction in the received noise!
  2. Replaced the ugly balun with a choke as above. No significant change noted in noise floor.
  3. Replaced 30 feet of RG-8x feed line to the shack with 30 ft of RG-213 coax. No significant change in the noise floor was noted. this change should help in reducing losses though.

Adding the choke to the antenna input made a big improvement in lowering the noise floor. I adjusted the Timewave ANC-4 to further try and negate any remaining noise.

So the results are as follows after 20m WSPR was run for 24 hours:

wspr1wspr2

Pulled ahead of N5CEY by 8 unique spots and made the DX list still lagging a bit behind Cliff. Here are my spots during this period (right image is Cliff’s and the one on the left is mine):

2018-03-18 (1)2018-03-18

So all in all a significant improvement by addressing Common Mode Currents. More on the Chokes in an up comming post.