Tuesday, October 16, 2018

Building a simple Receive Loop Antenna for SWLing

Many months ago I built a few differnet Hula Hoop based receive antennas and was pleased with the results.  I decided to build another one for a friend and will try to document the build in this post.

When I built the first one I built I also built a pre amp but have decided to use just the loop (passive design) for the last two I made. Here is a link for the design of the first one I built. This is the one I use on my SDRPlay.

For the passive design I bought the hula hoop (the adult model which is 36 inches in diameter) from the local Wal-Mart for $6.34.

The hula hoop
Be carful when choosing a hula hoop as some of them have lights in them and cost much more. The cheaper the better.

Once you have the loop, separate it at the seam. Once separated pull the loop apart and dump the water or sand out of it. I usually give it a few days to dry out which is easy in the dry climate of Colorado.

Find the seam

Pull to separate (could take some effort)
Do not throw away the plastic part that joins to two halfs together. You will use this to figure out which FSC box will work. I found the perfect one from the local Big R along with two pieces to join the half of the loop to the FSC box. You should be able to find this at any hardware or home improvement store. I also picked up a cover for the FSC box. Total cost was $10.06.

Save the plastic part in order to find the right size FSC box

One end of plastic insert matches the hula hoop part and the other fits the FSC box

Taking the foil off this hula hoop one proved to be more of a task than other ones we picked up. It was a lot more effort than I was prepared to give in one setting it so I attacked it a bit at a time. In the mean time and since the weather was cold and snowing I prepped the box for the coax connector. 

I found a coax connector in my junk box as I have used a lot of these over the years for various projects. They should be fairly easy to find and if you don't have one I am sure a local ham would be able to help out.

Junk box connector
Prepping the box for the coax connector is straight forward, just drill a hole and mount it. I had to use a file to get it to fit all the way but it is done.

Hole drilled into FSC box for coax connector

Coax connector attached

The inserts next to the FSC box
I think you can get away without using these plastic inserts but they just make it easier because once you have this all together the loop should stay the way you want it. I do add glue to these inserts to help and also use a screw in both ends to ensure no movement.

In this picture I put the ends into the loop however, it is better to run the wire in the hoop first as it will get caught on these things later and prove to be difficult.

I found some left over wire from when I built the UHF and VHF Egg Beater antennas and used that wire (about 10 gauge I think) as the inner part of the loop. You can use just about anything to include old coax.

In the next step I ran the wire through the loop then soldered it to the coax connector in the box. After this you just button the box up mount the antenna, hook up a coax and radio and your ready to start listening. Just for added stability I use a couple of screws through the plastic connector to make sure the loop stays upright if mounted from the box.

Wood crews on both sides for the loop for stability

All buttoned up, I just need to seal it and paint it.

You can find pre-amps for this antenna design on eBay and other places. I have built one off a design from the "Old Tech Guy" on youtube (a W7IUV design) and it works great with my SDR using the bias T off of the SDRPlay. I also built a pre-amp that I found on eBay and it works very well however, I really do not use it much for my other recievers.

This design, with no pre-amp, is what I use for the Kenwood R-2000 and the R-388 which work well with this antenna and it is just hanging from a plant hook under the roof of my deck. I have compared this to my receive only LNR End-Fed and think it is comparable in performance. Both are up about the same height (15 feet).

This is not a great antenna for pulling in the weak DX but it is great for general Shortwave Listening (SWL) which is what I use it for. Do not use this antenna for transmitting. It is just a compromise receive antenna. Rather than using a coax switch to connect one antenna to several receivers I would rather have each receiver on their own antenna and these work well due to the low profile and ease of placement.

Good Listening

Monday, September 10, 2018

Armed Forces Day QSL arrives

I still like getting QSL cards and I always look forward to the Armed Forces Day - Amateur Cross Band test and QSL.

NETCOM is not known for getting their QSL cards out in a timely matter but this year they did pretty good at about 5 months. I am sure it takes time to tally the QSOs in order to checkmark the ones you worked.

Here is this years card for the stations I worked.

QSL Front
QSL Back

In years past they sent a separate certificate (with SASE) for copying the DoD SecDef Message and I kind of miss that. However, the QSL is still a nice touch.


Friday, August 3, 2018

FOBB or Flight of the Bumblebees 29 July 2018

This year was special since FOBB fell on the XYL's (KC0YQF) birthday. We had already planned to be on our property but instead of fire mitigation and general cleanup we relaxed and I got to play in FOBB as BB number 1.

The McIntyre Wildlife Wilderness Study Area boarders out property and while Lookout Mountain is about three miles away we got a late start and decided to operate from a closer location.
Looking for a good spot

The view from our shack for the day

1. K9DXA in IL BB number 92

2. N5GW in MS BB number 52

3. AB9CA in IL

4. K7TQ in ID BB number 55

5. NK9G in WI BB number 23

6. N9NE/M mobile in WI BB number 75

7. KD3CA in PABB number 87

8. NG7A in AZ

9. WA8REI in MI (it is always good to hear my friend Ken on the air)

10. W7SW in AZ

11. N8XX in MI BB number 98

12. K0ZK in ME

13. WA7LNW in UT

14. WC6J in CA

15. KE9V in IN

16. K1SWL in NH BB number 36

17. N9XG in OH

18. VE3LFN in ON BB number 28

19. KF5RY in TX BB number 32

20. KD6L in UT BB number 101 (my only 40 meter QSO)

21. AC7A in AZ BB number 22

22. W7TAO in WA (If memory is correct my first QSO with Todd was during this event in 2012, we have had many QSOs since then)

23. N6GA in CA BB number 34

24. KA1UUM in NH BB number 115

25. K7MK in ID

I started to hear the storm on the radio and soon after the clouds showed up. As conditions got worse we packed up and headed out. No pictures of us operating as I was waiting until I was done but that was not a good plan. We made it back to the Jeep in the rain and headed out shortly after. There was still a hour left in the event and it was hard to secure but mother nature has a vote when you are operating outside.

I like this event because it is casual operating but still requires more skill than activating from a SOTA summit because you are not DX so to speak. I probably called at least 10 stations that did not hear me. 2 Band MTR, 9 volt battery and a good antenna works wonders at 8,000 feet in altitude. What fun!

Monday, July 2, 2018

SECDEF Armed Forces Day Message and Military to Amateur Crossband Test

Below is this years message from the SECDEF. This message was intercepted during the annual cross-band test using the digital mode called M110A that is available to Hams for download. Here is a website to download M110A by W3JJJ and I believe you can download it from the US Army MARS Website as well. The message was sent without encryption so Hams and shortwave listeners could copy it. It is signed by USMC Retired General Mattis which I have had the pleasure to hear speak when he came to Colorado Springs.

In addition to the SECDEF message there are several military stations that are on the air transmitting on military frequencies and listening on amateur frequencies. This allows hams to make direct contact.

Usually, after you have heard or talked to the stations you can fill out a form at the Army MARS web site and wait for your QSL card that shows the stations you made two way contact.

Due to budget constraints the responsiveness is somewhat slow and there is no more certificate for copying the SECDEF message which in my mind just takes a way from the event and while I understand budget issues there is a point where it becomes counter productive. I look at this event as one of the main Air Force MARS and Army MARS recruiting efforts of the year. It is important to make it as memorable as possible.

That being said, this year, station NSS sent out their own QSL cards to Hams that contacted them.

Today I received the QSL card and I have to say kudos or in Navy speak a big Bravo Zulu to the crew at NSS as they celebrated their 100th year since operations began.

73 NSS and Thanks


Sunday, May 20, 2018

Lookout Mountain and Fremont Peak

Lynn and I activated a few summits recently while stay on our land. We have not started building yet (need to do a well first) but do enjoy hanging out on our land and exploring the attached BLM land.

Lookout Mountain is on that BLM land and about 3 miles from our property as the crow flys.

Lookout Mountain ahead

Lynn making her way up

Looking back from the valley we approached from

Neat rock formations

Great views and the yellow wire is the antenna

Lynn operating SSB

My APRS Spot
The QSB was pretty bad. I heard KH7AL calling me but he did not hear me. I chatted with Al later and found out why. Al was using an AlexLoop antenna and those things just do not perform as well as a 30 foot piece of wire.


The next summit was Fremont Peak near Canon City. This trail system and summit is a best kept secret. The trails are great and you get views of the Royal Gorge along the way without the hassle of the tourist trap just a few miles away. There is also a well developed camp ground and it looked like a lot of people were taking advantage of it.

I forgot my cell phone in the car so no SMS spotting. I had the 2 meter and was able to spot Lynn with ease. I thought I had spotted myself as well but no go. 

Looking from the Peak towards the West at the cell tower

Fantastic views

The Arkansas River

APRS Beacon

That is all for now. I am working on a solar setup for Field Day and will report on that when I get it completed. I am also thinking of making a "For Sale" section of the blog just to weed out stuff I am not using anymore. Let me know what you think.