With Varying Frequency - Amateur Radio Ponderings

At Contest University 2008 the importance of this book was again stressed, and a discount coupon to buy a copy was part of the CU packet.  Here is my write-up & review of the book from 2007.  It is also being reposted as it was done before Tags and RSS feeds were implemented for this blog.

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At Dayton 2007’s Contest University one book on the important issue of station design for Multi Stations and SO2R (Single Operator Two Radios) Stations was mentioned by several of instructors.

Managing Interstation Interference by W2VJN

During the Dayton show I made a beeline to the INRAD booth to buy three copies - one for my local club, one for my Dayton traveling partner George W9EVT and one for my amateur radio library.

I found George W9EVT speaking with a long lost old time High-Speed CW contact who had worked Skeds for years between them. Imagine my surprise to find that with the books fresh in hand that this CW expert was none other than George W9JVN - Author of the Books!!

I mentioned how this book had received multiple mentions and recommendations during the Contest University and how I appreciated meeting the Author in person.

From the introduction of the book:

Whenever two or more transceivers are used in close proximity there is some level of interference involved. This level can vary from practically no problem to actually burning up components in the receiving radio. The purpose of this book is to identify and quantify the various parameters that create the interference and to show methods that will reduce or eliminate it.

My read of the book since Dayton has found that the CTU Profs understated the quality and usefulness of the information in this book. And that the book has not gone unnoticed by other experts:

ON4UN says:
“George [W9JVN] covers every imaginable
aspect of the interference
problem in this book…”

The actual stubs can either be designed and made by the amateur themselves, or one of George’s other businesses Top Ten Devices offers W2VJN’s Stubs as a commercial product:

Band Reject Coaxial Stubs
Every multi-transmitter environment suffers to some extent from harmonic interferences. In some cases, coupling due to closeness of antennas is sufficiently high that potentially damaging voltages may be present at the receiver terminals. Harmonics can be so strong that operation within 25 or 50 kHz is not possible due to receiver overload. Application of band reject coaxial stubs will reduce transmitted harmonics from the final amplifier and reduce fundamental pickup as well. This translates to fewer complaints from the operators, higher contest scores, and reduced risk of receiver front end damage.

Approximately 30 dB of harmonic attenuation can be expected from a single stub. Lumped constant filters can also provide the mentioned benefits, but none are available for amateur use unless they are home built. Top Ten Devices uses high quality RG-213 coax with a silver plated, teflon PL259 and heat shrink tubing on the shorted or open end. Rated ultra-conservatively at 1.5 kW continuous duty operation, these stubs will last a lifetime.

Stubs are manufactured to order and are individually trimmed with a Hewlett Packard network analyzer to +/-10kHz. When ordering, please specify CW or SSB, and the stub will be cut to plus 25 kHz from the sub band edge.

A single stub can be connected to the output of an amplifier with a UHF tee connector. For multi band operation, the stub(s) may be connected after the antenna switch. There is no requirement for a specific length of coax between the amplifier and the stub. Well shielded line should be used to prevent radiation of harmonics before they get to the stub. Two or more stubs for a given band may be used together. For example, a CS-4 and a CS-5 together will null 40,15 and 10. They would be connected with two UHF tee connectors close to the amplifier, if possible, to minimize pick up or radiation on the connecting lead. For stations where the amplifier is used on more than one band, automatic stub switching can be accomplished [and the] station antennas can be switched at the same time.

It is worth noting that not only has George W9VJN passed on what he has learned in his book, he is ensuring that his product knowledge & products remain available by passing the torch at INRAD. International Radio now in the very capable hands of new owners Trey, N5KO, and Mark, AG9A with George staying involved in the development of new products.

A recommended Book!

73

Steve
K9ZW

Ok, so from the start the CQ WW contest was never a main objective of a rapidly planned run to W9EVT’s QTH on Washington Island WI-001L.

But who would have planned for high winds requiring the towers to be down, extended rain to add to the fun, a laptop hard drive that went “ping” within hours of arrival, finding the Yaesu FT-950 DIN pins have nothing to do with any other Yaesu product making the cables I brought along useless to run a linear, sudden serious tower troubles with one tower that put the Mosely 96S, Bruce Array and Loop off line, and a couple bad commercially made co-ax jumpers that gave false SWR errors on certain otherwise good antennas while they were in use?

On the plus side I did get a fair bit of time with the FT-950 and a wonderful combination of the Ten-Tec Omni-VII and Expert Amp. Also spent quite a while operating the IC-7800.

The TimeWave AntennaSmith came in handy, though the foul weather kept towers down and operators inside so we didn’t get to work with the Riserbond TDR and the ex-Military Megger.

More over the next couple days after I unpack and sort something out for Laptop repair.

73

Steve
K9ZW

They say that what can go wrong, will. Well fortunately that is not quite true, but there does seem to be a correlation with the idea that the more trouble an equipment breakdown would cause, the more likely it will actually break down.

Within hours of arriving on Washington Island WI-001L my Macbook’s hard drive again bit the dust. As I had it loaded with the software I intended to use for the CQ WW Contest it is a bit annoying.

So going to my Palm I find that it has somehow ended up discharged. That it was perhaps helped by youngsters playing its feeble games might just have something to do with it.

Seems that one of the two cellphones joined the Palm in going flat.

Calling my Apple Store I learn that certain of the early Macbooks seemed to be jinxed with loosing hard-disks. With my copy of Leopard waiting for my return I sure wish this had happened a week down the road, when the OS-X 10.5 “Time Machine” would make loosing the machine’s hard-disk pretty much a non-event.

Oh did I mention that none of the Amp cables I brought along for the FT-950 will work either in the Linear Plug or the Tuner Plug? And that the QRP PSK-31 Setup I brought along depended not only on the computer that is now DOA, but on a cable I left on the bench at home?

On the plus side the Expert SPE 1K Amp is really neat!

The FT-950 has been getting great reports.

With some very welcome help from Hector AD4C the Omni VII is set up really well!

And that the footings and slab are in place for George W9EVT’s Shack Expansion?

More soon!

73

Steve
K9ZW

Scot K9JY had been doing a day-by-day looks at Contesting Tips that would improve a “Contester’s” enjoyment of “Radio Sport.” They would also help move their scores towards the optimum a Contester might achieve given their commitment, time and station resources.

After writing a contest tip a day for the month of September, Scot K9JY thought it would be a good thing to consolidate all of the links to the articles into a single article so people could easily reference each tip.

The resulting post’s URL is here:

http://k9jy.com/blog/2007/10/10/30-days-30-ham-radio-contesting-tips/

Any one of us interested in contesting would benefit from a read through Scot K9JY’s excellent checklist of contesting tips!

While you are reading Scot K9JY’s 30 tips series make sure and have a look through all his other fine articles!

Thank you Scot K9JY for the great work!

73

Steve
K9ZW

“Radio Contesting,” “Radiosport” or simply just “Contesting” is arguably the most agressive & competitive Amateur Radio undertaking.

Exactly what is it? 

Two great references are on the web:

Wikipedia on Contesting

AND

A very insightful look at Radio Contesting by Rick Tavan N6XI

Both good reads.

73

Steve
K9ZW

Finding it pretty hard to work much of the WAE Contest as we have a houseguest from the deputed land between England and Wales - the Marches of Monmouth.

Contesting, when I can get shack time, has been decent - a lovely wonderful contest, but annoying with the QTC’s (reciting your last ten log entries of a certain sort - my software doesn’t do them), but all in all great folk and lovely time.

Took our houseguest to a charity benefit “Rotary Lobster Fest”  last night, which was a hoot!  Good food, good music and a good time!  We went for Ice Cream at Cedar Crest Dairy, enjoying ourselves in the moonlight (well a little with the cresent) shadow of the Cedar Crest Dairy’s Huge Cow.

Hoping to get a bit more radio time…. 

73

Steve
K9ZW