Thursday, November 11, 2010

Our Community Leaders

I just received the December QST Magazine. There wasn't anything that really to terribly interesting and usefull for me in this issue again (sigh)... However the "It Seems to Us" editorial did catch my eye.... (here is a snippet)

Our Community Leaders

"Why do people become radio amateurs? If you ask new licensees, frequently you will hear that they are interested in radio technology or that they want to be prepared for emergencies and to provide public service communications. But there's more to it than that."

In general, people join groups with whom they have something in common and whose company they enjoy. Sometimes a desire to learn - to tap into a body of knowledge and expertise - is the motivator. At other times, sharing a common goal is enough to bring people together who might otherwise have no occasion to interact.

Amateur Radio is a global community. We can lay claim to being the first technology-based social network. The common goal that sparked the creation and early growth of the ARRL was the desire to develop a network of relay stations to overcome the limited range of the crude radio equipment of the day, so that amateurs could exchange messages with others well beyond the reach of their own stations.

Read the whole thing in the December QST, Page 9.

It's kind of interesting and fitting as I re-post this on a different social network. Oddly enough, where sharing expertise and knowledge doesn't require you to at the radio at the time of relay... A different demonstration of global communication nearly 100 years later.

It's also important to realize that the primary leadership role of a club is likely changing.

In the 90's maintaining a local repeater (or two) was the key to the local ham radio social network.

As more hams have since gained access to the internet and cellular phones, and now social networking sites online the repeaters are less active and less important.

It's time to step back and reevaluate the clubs role and priorities in 2010 and beyond.

And finally I have to repost this from Wayne Green's 11/01/10 blog:

A Ham Note

A note from Ben Alabastro W1VM chuckled over the September 2010 issue of QST having an article on a solar-powered repeater…and the Ham Radio December 1978 issue having an article on solar-powered repeater design. Glad to see you guys in Newington are still right on the ball.

Far's I can remember, our champions at the ARRL have never pioneered any new ham technology. To this day they're still pushing CW, a hundred-plus-year-old technology....

As pointed out, good leadership is hard to find at a national level. In summary: Local clubs really need to put more emphasis on leadership.

Wednesday, November 10, 2010

Tower Bonding & Repeaters

I recently helped a friend put up a Rhon 25 tower. We got into the discussion of what he might put on the tower. And proper grounding, etc.

This lucky guy got a hold of someone who had an attachment for a Hilti hammer drill to drive the 8 foot ground rods. (Notice the plural, as in two).

Years ago I wasn't able to find anyone with this so I did mine hard way.

Then I brought up the idea of relocating repeaters and such.

From the Hardware Noise section on
Without the proper grounding and bonding you may constantly be looking for noise sources. Pay particular attention to any point where two conductors are in poor contact with each other.

Tower bonding is something I didn't find a whole lot on when I did a google search.

Every 10 feet you have a semi-conductor. Snow and water do get into those joints on your Rhon tower, and over time there is light rust in those joints. This is a recipe for degraded repeater performance.

I showed this on an un-bonded tower that we once had our tech club repeater on.

We'd notice that on windy days, the weaker guys on HT's and such would have excessive creaking and popping on their signals.

So I keyed the repeaters local mic and went out and shook the tower as a demo.

Degraded noise floor.

After installing Copper Clad/ Zinc Grounding Clamps above and below each joint of the tower (as shown) this went away.

It's important to note that we also ran some RTV silicone around those clamps to prevent yet another water / rust joint. And finally spay paint them, as copper clamps rust easily.

There is a whole lot more I could write on keeping a quiet noise floor in duplex environments. But most of it has been covered elsewhere.

Most people don't understand how important this all is. I think this is because their experience is only in simplex operations. When you have something transmitting at the same time it is receiving the whole tower becomes like a charged capacitor.
This situation happens when transmitter power is put into the antenna and the surrounding area is lit up with the RF energy - yours or someone elses. What happens is the RF then creates tiny arcs and sparks in the broken joint and the receiver is desensitized by the wide band RF created by the sparking.

And RF Grounding is different than surge or safety grounding.

In RF, the length of the ground runs has much more to do with the fraction of a wavelength at the frequency involved than the DC resistance of the wire.

Good RF grounding can add several S units to the receive signal and dramatically reduce noise on the signal. Think surface area, and creating as big as RF counterpoise outside at your ground system.

Monday, November 1, 2010

Kenwood TKR-850 as a D-Star Repeater

In my opinion this type of thing needs more attention. After all do-it-yourself has long been a hefty part of this hobby. And there is no better way to learn than a hands-on project like this.

Reason number two would be economics, but I think that is obvious.

The third is spectral savings. D-Star is narrowband, but buying a new system just robs another frequency pair from the pool. It seems people rarely take repeaters off the air, even if nobody really uses them. And these days it seems there are more repeaters in a geographic area, than there is activity.

So it seems best in my mind to convert something already out there. This would make a great club project.

This is great example of continued innovation of D-STAR technologies by incorporating non-Icom products into D-STAR environment.

Date: Thu, 07 Oct 2010 05:32:17 -0000
Subject: K8BIG Port B Using Kenwood TKR-850 Interfaced to ID-RP2C

The K8BIG Port B D-Star Repeater in Cincinnati, Ohio is successfully running using a Kenwood TKR-850 Interfaced to the Icom ID-RP2C in place of the Icom Band module (ID-RP4000V). The usable range of the repeater has been effectively doubled from around 25 miles radius to 50-55 Miles radius.

The K8BIG system is on the WCPO-TV Tower overlooking downtown Cincinnati, OH with the antenna at 700' AGL. There are 3 50,000 Watt FM Radio transmitters, 1 250,000 Watt VHF DTV Transmitter, and 2 3,000 Watt LPTV stations on the same tower along with various commercial VHF/UHF/220 transmitters so the RF environment is pretty harsh - add in the neighboring (2 Blocks) tower with a similar complement of transmitters and it is downright brutal for any radio equipment.

The Icom band module was being swamped by the high RF levels at and surrounding the site, causing very poor effective receive sensitivity even after the TX-RX BpBr Cans and an additional band-pass cavity. I had partially remedied this with one side of a reject-only mobile duplexer, but that introduced around 6 dB of insertion loss. Even with the 6 dB insertion loss the effective sensitivity was improved. The Kenwood repeater has a much tighter front end and much better selectivity with adjustable front-end helicals so the additional receive filter is not necessary and the 6 dB insertion loss was removed.

After the interface was built we were able to plug and play into the Icom ID-RP2C controller and gateway. With the exception of the increased range there is no operational difference in the repeater - everything works identically to the Icom band module. Commands work, data works, D-Rats works, etc.

I will be building more of the interfaces shortly which can be used to interface any 9600 baud-capable analog repeater directly to the ID-RP2C. Anyone interested please let me know.


Dan Woodie

You may want to look at;
Michael, VK5ZEA's Homebrew DV Node Adapter to ID-RP2C interface.

John, K7VE's Kenwood TKR-820 Node adapter retrofitting.

And/or my Motorola GM300 retrofitting and commentary.

As a technical side note, one thing to consider when converting analog repeaters is the receiver IF bandwidth. To date there has been little discussion on narrowing receivers bandwidth to match the narrower D-Star signal. Just be aware that converting a 1950's era repeater to D-Star that might have a 60 Khz I.F. would be vulnerable to adjacent channel interference. A good overview of the theory can be found in a reprinted article from Ham Radio Magazine 1985, by WD5IBS.