Radio W4KAZ

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BPFF – The Guess-timated Scale and actual Guess-timates – Part 6

Part 6 of the W4KAZ filter project series discusses the actual measured S-meter calibration, and the filter attenuation estimated based on S-meter measurements.

As I meandered through Part 5 of this group of posts, I needed to find a way to calibrate the S-meter scale on the FT-920 to a 6DB reference. Lacking any real test equipment, this will allow me to do relative tests on the band pass filters to measure the filter attenuation on the harmonics and sub harmonic. So I used the attenuator pad(6,12, and 18db) to measure the delta between each S-unit from S-0 to S-9, “10 over S-9” and “20 over S-9”.

Big shock(NOT!): The S-meter on the FT-920 is definitely not linear.

Actual Big shock: The S-meter actually IS linear over part of its scale. I was a bit surprised by that.

The S-meter on the FT-920 was “measured” by using the attenuator pad, inserting attenuation and noting the S-meter drop. It came out to something like this:

S0-S4 – 6db S4-S5 -6db S5-S6 – 6db S6-S7 – 6db S7-S8 – 6db S8-S9 – ~9db S9-10 over 9 – ~12db 10 over to 20 over – **Not measured**.

It was hard to decide if the drop from 20 over 9 to 10 over 9 was 12db or more, so I didn’t do any testing with any signals that strong. For the sake of an example, when the original signal was reading S4, adding 6db attenuation dropped the reading to S0.

It seems noteworthy […]

Continue reading BPFF – The Guess-timated Scale and actual Guess-timates – Part 6

Field Day and The K3NG HomeBrew Rain Fly

With Field Day right around the corner the K3NG Home Brew Field Day Tarp Canopy seemed timely. I don’t have(i.e. “will not have”) a google account, so I couldn’t post comments to K3NG’s post. But it’s cool enough to bookmark permanently. Literally. Putting shade on the tent keeps the operating position much cooler.

My initial reaction was that K3NG’s cover would be subject to water pooling. As I kept reading, I saw that he noticed that too. Back in the swamps as a WB5, we used a similar strategery for shade and rain. Rather than risk poking holes in the tarps with center supports, our solution was to make the front posts about 18 inches longer than the rear posts. The slope was sufficient even in a heavy rain.

Our own posts were cut from pine saplings liberated from one of the club member’s farm.

With the front facing north, that also helps throw the shade a bit lower on the tents below the cover. It works pretty well at shedding rain too. Lots of chances for rain on Field Day when you are only 20 miles off the Gulf of Mexico. Ick.

O’course, it rained about three inches here at the NC KazShack Tuesday morning. My front yard becomes a small stream in these conditions, with water flowing over the driveway, down across the yard and over my neighbor’s driveway too. So much for the landscaping. Landscape timbers, mulch, even the grass – whoosh.

I sure hope the wx […]

Continue reading Field Day and The K3NG HomeBrew Rain Fly

2008 FD Results For N4PY

The FD results for the 2008 FD were put online back in February. But as we bear down on FD 2009, time to review. The N4PY crew managed to win the Roanoake Division in class 3A. We finished in 10th place overall of class 3A., and 63rd for all entries regardless of class.

Not too shabby for seven guys in a completely new and untried location.

We were beat out locally by the OCRA crew, who put up a really good score operating in the 5 watt battery class. Also K4QPL squeaked by us with about 50 more QSO’s in class 2A, although we had more points.

But on a “QSO per Peep” basis we did rather well. There are only a handful of other stations that managed to lay out as many QSO’s per person with as few people as we did. Most of those were two man set-ups. Sweet.

Maybe if we find a BBQ staff N4YDU will be able to add another 1000 Q’s to the total.

1st of 8 and of 21 ,class 3A, in the NC section andRoanoke division 4th of 73 overall in the NC section 11th of 188 overallin the Roanoke Division 10th of 303 in class 3A nationwide

cqfd cqfd cqfd…..

Contesting Webinar Schedule

Jamie, NS3T, has posted a schedule of the PVRC Contesting Webinars on

This is the beginning in what is expected to become a series of webinars going forward, focused on the contest community. This has a lot of potential to be a great resource for folks who may haveinterest in the subject matter, but not the financial resources or time to take part in other venues like the Contest University.

The webinars scheduled are open to anyone, anywhere.

For details see:

BPFF – Guess-timating the Filter Efficacy – Part 5

Part 5 of the W4KAZ filter project series discusses filter losses, an idea for getting a very rough S-meter calibration, and trying to estimate the out of pass band attenuation provided by the filters.

The Losses:

The filters do have losses in the pass band. This is known as the insertion loss, and is reported in db. When discussing the pass band, we want the losses to be as low as possible, or approaching 0.0db of loss. The old rule of thumb is for every 3db of loss you are losing about half of your power. So, 100 watts of RF transmitted through a 3db loss component means there is only 50w coming out the other end.

Run that through the loss formula…. db loss = 10*[log(100/50)] = 10*log(2) = 10*.30103 = 3.01db of loss.

Since loss is defined as a ratio of the actual power levels, a simple watt meter and dummy load can be used to measure the losses of a component in db. That gives a nice yardstick for comparision to known commercial filters. The accuracy of the wattmeter is an issue, but part of the game is to compare the values I come up with against values measured with better test equipment. If I ever manage to hook up with one of the guys who are willing to help with that.

The set up to measure the loss in the pass band is simple.

Transmitter–> filter –> watt meter –> dummy load

By replacing the filter […]

Continue reading BPFF – Guess-timating the Filter Efficacy – Part 5

Home Brew Projects Page

Time for a centralized list of home brew projects. So all of the following have been listed on their very own page linked in the sidebar to make it easier for me to find them.

SO2R related: Band Pass Filters(a series of postings) SO2R Box – Engineer the Possible Band Decoder Other: Using PL-259’s on CATV F11 Simple Two Position Remote Antenna Switch Other Remote Switch Project Ideas Yet more Remote Switch Project Ideas Elecraft K2 Cooling Fan Useful Parts List Home Brew Station Desk CW Touch-Keyer kit G3TXQ BroadBanded hexagonal Beam Home Brew Knobs Seven position remote antenna switch K9AY box RX antenna 160m/80m band splitter


WPX CW 2009

WPX from the cheap seats……

I was a little disappointed at first, since I missed most of the better band conditions. Mostly operated during the early evening and both afternoons. After a good night’s rest and most of a week later, it turns out the contest looks better than the first impression.

This contest was mostly a shakedown cruise for a lot of shack and antenna system changes revolving around setting the place up for SO2R. The shakedown was a success.

All of the home brew items seemed to function well. One minor glitch in the SO2R box. It would appear that I managed to wire the left and right channels reversed. Good thing the headphones I prefer are “ambidextrous” – that work around was easier than sitting backwards. 😮

Two sets of home brewed band pass filters worked well with low power, even though the KazShack antennas are practically touching one another. The set of K4VX filters were augmented with coaxial stubs. The worst case interference is between 40m and 20m, where the harmonic is about S6. 80m/40m are completely free of any interference, and 40m/15m are also friendly.

The big lesson learned was that SO2R will be a lot of fun, once I become proficient at SO1R. It became obvious that I am NOT yet a proficient operator, not that I had any doubts there. It was great to be able to S&P while running at low power, but I did flub some Q’s on the run radio […]

Continue reading WPX CW 2009

BPFF – The Kludgy Switch Box – Part4

Part 4 of the W4KAZ filter project series comments on the process leading up to the integrated box full of NVARC Ugly filters for use in the KazShack. The quest continues.

Notes: Link to photos of the project at bottom of this page. If you want to read about the project from the beginning, go to the”Band Pass Filter Fever” series page.

Part of the project goal is to put all of the NVARC filters into a switched box to allow for SO2R and use at Field Day and on IOTA expedition. The original idea was to use a simple rotary switch. Somewhere along the way the idea morphed into using relays set up to allow control from a band decoder.Toying with the relay switching idea brought up a couple of issues that I chose to avoid. Instead, the individual filters were tied together with a two pole ten position switch.

A previous project resulted in a seven position remote antenna switch.That switch is lossy on 15m and 10m because of the point to point dead-bug style wiring. I didn’t see an easy way to avoid this problem, and I’m not set up for PCB design/manufacture. Using PCB’s and strip line runs would solve the issue. I have an idea for making strip lines that may work, but it is a bit Rube Goldberg-ish, so I chose to shelve that temporarily.

So, back to the rotary switch. I had a 2-pole 10 position switch in the junk box. The contacts […]

Continue reading BPFF – The Kludgy Switch Box – Part4