Posts Tagged ‘coax’

Coax losses

If you are like me, then you always want to know the loss of your coax at 6m,2m and 70cm, possibly higher I found this very useful table to compare various coax cables at different frequencies. You may have your own favorite table! If not, I hope you find this one useful.

See http://www.w4rp.com/ref/coax.html .

The best laid schemes o’ Mice an’ Men

To quote Robert Burns
The best laid schemes o' Mice an' Men, Gang aft agley,
An' lea'e us nought but grief an' pain, For promis'd joy!
That sums up my weekend perfectly.

After becoming licensed my eagerness got the better of me and in a moment of weakness I'd purchased a couple of 10m ready made cables from a major supplier only to discover quite quickly they were made from low grade RG58 coax (you can literally count the number of strands in the braid) and the connectors while serviceable were so poorly fitted they fell off!

James that PL259 has fallen off again!

I had refitted the connectors using some solder this time and had managed to blag a 20m length of good quality RG58 (this actually has some braid) and I am ashamed to say these cables have been the weak link in my set up for far too long and needed to be upgraded.

I also needed to sort out the mounting for my aerials. Up till now I have been using a 5 meter telescopic painting pole that had cost around £16 from B&Q, it was okay when I was just clamping one aerial at a time to it but with the purchase of the rotator I has been chancing my luck with the loading, narrowly avoiding catastrophe when pushing the pole. I also couldn't fully extend the top section as the tube and joint were potentially weak. It was guyed quite well but was far from aesthetically pleasing, even in the summer sunshine!

6M Moxon up on temporary pole
I couldn't fit anything to outside of the house, not only for logistical reasons but also it wasn't sanctioned by the station manager. Anything on the side of the house would be highly visible from the road and the back wall of the house has too many large windows and an extension making it inconvenient to fit and access anything.

Never fear I had a plan, a 20ft (6m) scaffold pole bolted using swivel joints on to to an another pole concreted in the ground in the back garden. The garden was extensively landscaped a few years back but it was before I became licensed, so I hadn't planned ahead. With careful negotiations with the station manager I secured a location where I could put it.

Thanks to my local handy man I now have two 10ft scaffold poles, sunk to a depth of nearly 5ft and encased in concrete in the corner of the lawn. A few inches of soil was left on the top to allow the grass to grow. They have been left for over a fortnight to completely set.

Scaffold pole sunk in ground

I ordered a 100M reel of RG213 coax from Nevada Radio along with plenty of high quality N-Type connectors and various clamps and intended to sort out my antenna set up this weekend and banish the abysmal RG58 coax and PL259 connectors to some dark corner of the shack.

Before I took everything down on Saturday I managed to make contact with GB0TDF the special event station being run by the Denby Dale Radio Society from Cartworth Moor, Holmfirth for the Tour de France Grand Départ

A few months back I picked up a cheap rotator at the Dambusters Hamfest. It is designed for television aerials and isn't heavy duty but I was sure it would cope turning with the small 2M, 70cm Yagi and a 6M antenna on the same pole, with the X-50 collinear on the very top. However I was concerned by the potential lateral loading.

The rotator is a generic design and I spotted that an optional support bearing is available as an accessory. I chanced on one via Ham Radio Deals and had salvaged several good lengths of galvanised pole from a skip where I work. So the plan arrangement was as shown.. simple right? 

Planned arrangement

It turned it a frustrating morning after cutting the metal pole to length, bolting and clamping everything together I tested it at ground level with no antennas and the rotator refused to turn correctly and I narrowly avoided burning it out.

I checked poles and they were true, the rotator was free running as was the bearing. I unbolted, fettled and just couldn't make it work. I went away and had a beer while watching some of the Tour de France on the TV and in a moment of clarity realised what the issue was.

The problem was the diameter of the salvaged pole I was using. It was was slightly narrower (a couple of millimetres) than the hole in the bearing. I'd assumed it would line up with the rotator as it was similarly clamped, however when all clamped up top and bottom the pole wasn't perfectly perpendicular and wouldn't turn due to the eccentricity, Hopefully the drawing illustrates the problem.


Annoyed by this basic school-boy error I reverted to Plan-B for the short term, no support bearing! I was in bad mood now and so decided to leave the rewiring to another day. So I quickly put the 2M yagi on the existing coax as a test on the new scaffold pole to make a few contacts for the VHF NFD.

Temporary installation to test scaffold pole

Walking up the scaffold pole is straight forward, I have bolted a small cut off of scaffold across the top of support poles to act as a safety stop, lowering it likewise easy and I will certainly build up the muscles!

I managed to grab just 8 QSOs but was otherwise engaged for the rest of the weekend, however I was encouraged by the distances.
I hope to get the 70cm antenna up tonight on the RG513 ready for the 432MHz UKAC on Tuesday evening.
The birds like the new setup




Time for some radio now

I’ve spent far too much time putting this blog back in line thanks to some dodgy code that got into my site. The site as a whole has shrunk a bit and I’m adding content back in as I go along. Its all very time consuming even though I have loads of back ups.

Having said that I’ve found a bit of time to do some planning for the new mast and feeders etc which I’ll order as soon as I get firm quotes for the building work I need to do for the extra room. Scam 12There’s still a bit of a battle at home over the position of the thing which looks a bit like this one. They are fairly compact masts in as much as they are telescopic but pretty heavy too at 80+Kg.

Plans are to make up a tilt bracket and to mount it on the side of the new room (with enough space for a decent beam in the future).

With it being telescopic the feeder needs to be carefully considered so it doesn’t fracture from being raised and lowered regularly. This is part planning application and part saving antennas from strong winds and salt spray. Ideally a good quality VHF coax will be used for yep, VHF antenna’s but getting the right one is crucial to avoid expensive mistakes. Time for a chat to the DX shop I think.

Show Notes #097

Introduction:

  • Welcome to another episode of Linux in the Hamshackedness, where the Chocolate Shake Fairy visits Richard.

Announcements:

  • LHS now accepts micropayment donations via Flattr. It’s been successful for the Linux Outlaws guys, so we’re giving it a try here.
  • We now have a countdown timer on the Web site that shows the time remaining until the next live recording. Of course, now that we’re recording on Wednesdays, we’ve decided to move back to Tuesdays. That will happen in January. Keep an eye on the web site for the dates. (Tuesday, January 8, 2013, as of this moment.)
  • We also have a Google Community for Linux in the Ham Shack. It’s a great method for leaving feedback, show suggestions, questions, hate mail or anything else.
  • The Dayton Hamvention 2013 will be coming up soon, so we’ve added the donation thermometer to the website. Please make a donation and help send LHS to Dayton again in 2013.
  • Sign up for the LHS mailing list, too.
  • Gnorman has a bio on the LHS About Us page.

Topics:

  • Raspberry Pi in the Ham Shack
    • Russ has been working on getting an Echolink node running on his Raspberry Pi.
    • He’s chosen Raspbian as the operating system, which is based on Debian Wheezy.
    • Installation consists of downloading the iso, using dd to copy it to a secure digital card (SD flash memory card), booting the Raspberry Pi with the SD card, and following the prompts to install.
    • VK2MEV has posted instructions for configuring a Raspberry Pi as an Echolink node.
    • So far, Russ has Raspbian installed, as well as svxlink and qtel, but has not yet connected it to the usb sound card or attached it to his Rascal GLX interface to control the radio. Another option would be to use the Pi’s GPIO bus to control the radio instead of a digital mode interface.
    • VK2MEV also has a page describing WSPR on a Raspberry Pi. (Another page is VK2MEV’s blog on WSPRnet.)
    • Ted, WA0EIR, says he thinks some folks have his PSK31LX program running on a Raspberry Pi.
    • Russ mentions that there is a Slackware build for the Raspberry Pi.

Feedback:

  • Cory, KD0QEA, asks if there are any “hangout” radio frequencies for LHS hosts and listeners. Well, Cory, there are none due to lack of time for the hosts to get on the radio. However, perhaps our listeners would like to establish an LHS net. Email your suggestions for bands, frequencies and times and we’ll announce them on the podcast. When Russ gets his Echolink node/Raspberry Pi running, he’ll be there more often. The node number will be 54711 (LHS11 on the telephone pad).
  • Doug, N6LMX, left a voice mail about the Raspberry Pi. He has one and wonders which ham radio apps can be used on the Pi. He’s also using Raspbian as the operating system. Doug will be attempting to create a media center with his, as well as ham radio applications. Russ suggests running the Pi headless and using ssh from a smartphone or tablet to access it. That would avoid having to carry a monitor and keyboard around with the Pi. It’s likely that most of the popular Linux ham applications, such as fldigi, would work fine with the Pi, though you may need to compile them yourself. As for the media server idea, the Pi may not be quite powerful enough. Raspbmc is based on XBMC, and might be the best option. Ted, WA0EIR, has several Linux ham radio applications that should work quite well on the Pi. Richard also wonders if there are folks running APRS on the Pi, and there’s at least one. Thanks for the voice mail, Doug. We appreciate it.
  • Dave, M0DCM, has been catching up on the show, and responds to episodes 95 and 96. He uses 75-ohm coax as a feedline with a 1:1 balun to horizontal and vertical dipoles, and is able to bypass his tuner on 21 and 24MHz. He goes on to describe his Linux and radio activities. Thanks, Dave.
  • Thanks to everyone who sent happy birthday messages to Russ.
  • Gorkon, aka Joel, says there may have been a problem with the ogg version of episode 96. Russ will take care of it if he finds the problem.
  • Mike, from Sugarland, TX, has been trying to use N3FJP’s Amateur Contact Log (ACLog) program for logging, presumably under WINE, but it crashes and he wonders if anyone else has had any experience with this. If any of our listeners have tried ACLog under Linux, let us know, or respond on the Google+ LHS community. Russ suggests forcing WINE into 16-bit compatibility mode.

Contact Info:

Music:

  • None this episode.

LHS Episode #097: Sheer Hamshackedness

shack-03Welcome once again to the Wonderful World of Linux in the Ham Shack. As indicated in the title, this episode is full of Sheer Hamshackedness. If you’re unsure what that is, we encourage you to pour yourself a nice glass of dark beer or a 100-proof spirit of your choice, put on your headphones and immerse yourself in the pure hedonism that is LHS. And if you believe any of that, we have a large vehicular conveyance over the East River in New York City up for sale as well. Anyway, we talk a little bit about Raspberry Pi computing, APRS, WSPR, Echolink, svxlink, Qtel and a bunch of other stuff in this episode. Hope you enjoy, as always.

73 de The LHS Guys


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