Tuesday, 27 June 2017

Versatile FSQ digimode

Last weekend there was the fieldday. Julian OH8STN noted on facebook he was going to be QRV portable digital as his personal fieldday. I wrote about Fast Simple QSO digimode before. I tested it with Julian that time also with success. This time besides Julian there was a norwegian station LB9YH involved as well. We actually received each other very well. But....it would be nice if for example in a weekend of choice there would be a couple more radio experimenters on to test FSQ. If you're only want to make QSOs for your logbook this experiment is not interesting for  you as there is no QSO involved, only a connection to other stations. If you are interested this piece of software is easy to understand but has a lot of features you can experiment with...

So I was thinking. When there is a huge distaster or war going on and there is no internet anymore, no telephone, no "commercial" radio or TV even no electricity. I know, that is really worse....
We as hobby radio operators still have possebilities to send our messages, fax, pictures, files and whatever information you like. But what about those systems like Winlink and PSKmail which are widely used by emergency nets? They don't relay messages without internet as the "servers" are just relaying from air to landlines. No, you really need a simple independent system which can run individually or as a kind of network free for everyone with a amateurradio license to jump in without any membership, payment or code. I think FSQ comes close to this system.

So I downloaded and installed the newest version of FSQcall, although you can run FSQ also in FLdigi (FLdigi can run on both Windows and Linux). It really is a simple to understand program and most things are automatic. The interesting thing is that you can use a number of commands to get information from the station you see without intervention of the other operator. For example your signal report, location from the other station, a webcam image, fax, files etc.

FSQcall can be found on: http://www.qsl.net/zl1bpu/MFSK/FSQweb.htm
You can also find a powerpoint here which compares FSQ with pro ALE systems that are in use for example in the military.

FLdigi FSQ configuration here: http://www.w1hkj.com/FldigiHelp-3.22/fsq_configuration_page.html

I was planning to make a video but KB9RLW Kevin has already done it. You get a impression....

If you like to install the program yourself to experiment it could be wise to click help and read the FSQ introduction first.

Calling Frequencies

Region 1 (Europe, Africa, the Middle East and Northern Asia)
80m     3588 kHz USB (sunset to sunrise)
40m     7044 kHz USB (sunrise to sunset)
30m    10144 kHz USB (local day, DX night)

Region 2 (The Americas)
80m     3594 kHz USB (sunset to sunrise)
40m     7104 kHz USB (sunrise to sunset)
30m    10144 kHz USB (local day, DX night)

Region 3 (Asia-Pacific)
80m     3580 kHz USB (sunset to sunrise)
40m     7105 kHz USB (sunrise to sunset)
30m    10149 kHz USB (local day, DX night)

Friday, 16 June 2017

The PL259 myth

You often read or hear that every PL259 connector on your coax adds 0,5dB loss. This might be the truth on UHF and higher. But on HF/VHF that's not the case.

Recently I was thinking about the 50m Aircell7 coax I run to my antenna now through a homemade disconnect/patch panel. So, this coaxcable to my HF antenna contains 4 PL259 connectors and a female/female barrel to connect the 2 pieces. 50m Aircell7 has a loss of about 1,8dB on 28MHz and 2,4dB on 50MHz. I've no interest in VHF/UHF so leave that out.

At the new antennamast I want to have another patchpanel at the bottom of the mast like I had before in my previous QTH. I want to add some lightning protectors and a galvanic isolation transformer for the highest (HF) antenna in my mast. Now I was afraid all the PL259 connectors would add a significant loss to my transmission line. But after all I think it is not that much.

Steve Katz, WB2WIK/6 demonstrated at the Dayton Hamvention in 1985 that the loss in an 83-1SP PL-259 connector averages .0435 dB per connector at 28 MHz.
The primary difference between a "zero loss" PL-259 installation and a lossy one is how the connector is installed

PE4BAS experimental test site
However, I'm not a believer. I like to test this out. Although I haven't any high sensitive equipment, only my trusty MFJ-259B. Is the PL259 loss a myth or can I bust this? I did some test this evening and made some interesting discoveries.

My not-so-scientific test setup: MFJ-259B, 2 pieces of 10m long Aircell7 coax laid down in the too long grass with PL259 connectors both sides. Only soldered at the center. Braid is screwed into the connector when I assembled it in 2005.

10m Aircell7 has a calculated loss of 0,36dB. 2 PL connectors have a calculated loss of 0,087dB = 0,3687dB (0,37dB including the female/female barrel connector). Total loss of the 2 pieces calculated 0,74dB. Lets see:

Left: 1 Piece of coax - Right 2 Pieces connected
Of course the MFJ-259 is not very accurate and has losses itself. However, this is not a bad result.
Ready to do a practical real life connector test...

13 connectors in total
I connected the 2 pieces of coax with as much connectors and connecting barrels as I had. Besides 2 times PL259 I added 11 connectors. This should add a calculated loss of about 0,4785 dB (0,48dB). But in real life it only add 0,1dB.

Another test....add 4 times a 90 degree connector. Now this is going to be serious!!! There could be a faulty connector. So test just one of them:

Still higher loss. 1 90 degree connector 0,7dB loss,  The 90 degree corner does probabely affect the impedance of 50 Ohm?

PE1BVQ Hans is always searching for silverplated old PL (and other) connectors at radio rallies. Preferable the original amphenol ones. I asked him why, he says they are the best, others can add a lot of loss in your system. Could that be true? Or is this another myth that's going to be busted?

Let's see:

I changed the 90 degree connector for a silverplated original Amphenol one. Gone is the loss! How strange is that?

Well, of course I don't use any superduper sensitive low loss equipment but it shows that there can be a difference in connectors. As long as the connectors are mounted in a straight line it hardly gives any loss. Very important of course is a good soldering connection between the coax and the PL connector.

A few tips:

* Solder both core and braid. Best way in my opinion is how it is done by K3LR.
* Keep connectors clean so they can make a good lossless connection
* Tighten them well. I checked that as well this evening, a loose connector gives about 1dB or more loss and propabely a lot of unwanted RF around the loose connection!
* Prefer silverplated (Amphenol) connectors, they probabely are the best you can get.
* Amphenol too expensive? Look for them on radio rallies. I payed about 50 cents for the 90 degree connector.

Thursday, 8 June 2017

The 6m band holy grail

For us here in Europe the holy grail of the 6m band would be working Japan on 50MHz. There are several thoughts about how a distance like this can happen. But at least you need ES propagation or Sporadic E just what you like to call it. This happens only a few times a year and only at a small timeslot around 9 UTC it is possible to hear and transmit your signal to Japan. There are years that this doesn't even happen at all. With JT65/JT9 mode it is a lot easier to spot Japan, but a QSO is still difficult as the JT modes are just too slow. However I managed to spot a few Japanese, best distance was 9125km spotted JR2WYD. My neighbour PA0O even worked Korea on 6m for the first time in his 30 years DXing on the 6m band!  I was surprised I spotted DS4EOI from Korea today at -16dB myself, that's a great signal on JT65! Think of my antenna system which consists of my Watson W2000 triband at only 6m height and 3 pieces on Aircell7 coax all connected through PL connectors. Crappy 6m setup you would say. Imagine what could happen if I had my mast and 5 element 6m yagi up!

Another spot intrigues me. N6ML at that time of the day. Strange propagation....