Entries from October 2012 ↓

Wire Antenna

I finally got my last wire antenna trimmed out and up.

It is a half wave on 80 and fed at about 1/3 way from one end. One leg is 45 feet the other is 90 feet. The thing is similar to a Windom. Covers multiple bands without a tuner. Drive point impedance is around 300 ohms. I have a 4:1 balun at the feedpoint and run 50 ohm coax from there.

SWR around 1.5:1 on 80, 40, 20, 17, 15, 12, and 10.

SWR 3:1 on 75 and 3:1 0n 30.

I can put a 100pf capacitor in series with the 90 foot leg and that is supposed to bring the SWR on 75 to 1:1 without effecting the other bands. The only band that will not be covered is 30 meters.

Other than being able to use one wire on multiple bands without a tuner there is nothing special about the antenna. Just a 1/2 wave on 80 meters. The radiation pattern gets a little complicated on the higher bands. Multiple lobes especially on 10.

Going to hook this antenna to the Yeasu amp and Omni. With the 950 and 922 going to the antenna switch selecting the 75 meter dipole, beam, and inverted-L.

Buying used Tubes

In a single word, DON’T. If you must buy used because new tubes are no longer being made reconsider the advisability of continuing to use the equipment requiring that tube. If you still want to continue with the tube purchase try to get some sort of guarantee.

Broadcast and medical pulls still have considerable life left and can be good values as used as long as the price is less than half what a new tube would cost. Used tubes are not worth more than half the price of a new tube and possibly less than that.

Tubes that are still being manufactured and available as new are always preferred as long as they are exact substitutes for the tubes being replaced. Note that there are tubes being produced by foreign companies that claim but do not provide compatibility. Among these are 572 and 811 and, no, you can’t rely on the new spec sheets. Look for help on the internet from people who have already been burned.

Normally you should have no problems buying from reputable suppliers like R.F.Parts. They provide a warranty and money back guarantee.

Under no circumstances should you buy anything that may require filament or cathode conditioning. In fact I would not waste my time on these even if they were free. The chances you will end up with a dead bulb are too great.

Parts Radios

I see more and more ads offering ‘parts radios’ usually at unrealistically high prices. To a buyer, a parts radio is a non-working chassis duplicate of a non-working radio he has which needs repair. His hope is that the ‘parts radio’ contains the part he needs and that the needed parts are still good. The seller merely wants to retrieve the last thin dime from a bad investment or operator error.

If the subject radio died of natural causes, the ‘parts radio’ most likely suffered the same fate. I other words, the parts that are bad in the radio needing repair are most likely bad in the ‘parts radio’ as well and the buyer has a good chance of becoming the proud owner of two broken radios.

It could be that the ‘parts radio’ quit working right after its operator applied reverse polarity power to an unprotected circuit. In that case the smoke was let out of most of the components that made the radio work and we have a ‘parts radio’ full of bad parts. In any case, chances are pretty good that the ‘parts radio’ is not repairable, at least not by the seller since he has obviously given up on it.

By ‘repairable’ I mean that it would take less time and resources to fix the broken radio than it would take to buy a new one. If the time and resources to repair cost more than a new radio, you should not be playing with ‘parts radios’

Parts radios are not entirely worthless. They all have parts that are not smokeable. For instance, knobs. I have never seen anyone talented enough to let the smoke out of a knob. Most average radios may have up to a dozen knobs worth at least fifty cents each. That is a total asset of $6 maximum and that is all you should ever pay for a ‘parts radio’. Then all you have to worry about is if it is worth the shipping cost to find out how much damage was done to the ‘parts radio’ to make it quit working. You know it will be double boxed, properly packed and treated well so it won’t get damaged in shipping, right?

There are few things less rewarding than paying good money for someones trash and paying extra on top of that to have it shipped to you when it should have been given a decent burial at the sellers location.

There is a huge difference between trash collecting dumpster divers and trash buyers. You don’t want to pay for trash and end up having to dispose of it later at additional cost.

Browser Problems (Firefox)

I use Firefox if I want to watch Netflix movies on my Windows computer.

The other day I started Firefox and up came a window with a blue line and tiny Firefox logo but everything else was blank.

I fiddle fumbled around with that for a while and got a message that some profile file was missing or not found.

Apparently this is not an unknown problem. A search on the internet showed others having the same problem. The only thing missing was an official fix from the Mozilla folk. They did offer a beta version of a stand alone profile manager. By using that manager and bringing up Firefox in safe mode I was able to make Firefox work again. This was after I spent a day uninstalling and re-installing various versions of Firefox without success. I also disabled various add-ons without effect.

Evidently uninstalling Firefox does not nuke all the Firefox files. Previously selected options and bookmarks were still in place in the various reinstallations. I was glad not to have to reinstall bookmarks from backup but I also made a note to manually cleanse the drive in case I wanted to rid my system of Firefox in the future. Firefox uninstall does not do a complete uninstall.

Another interesting fact is that as Firefox has grown larger with more features, add-ons have also increased in number with most of them offering to interfer with the new features offered in new revisions of the Firefox software. Apparently some new features put privacy at risk. The add-ons offer to restore the lost privacy.

Since I have no interest in Firefox other than needing it to watch Netflix movies, I certainly don’t need all the new features in the latest release. I particularly do not want to take time and resources to add software add-ons to allow me to disable features that I did not want in the first place!

Not interested in bloated software offering features that I would later have to add even more software to disable those features, I decided to go back to the earliest version of Firefox that would allow me to use Netflix.

I installed that earlier version of Firefox and installed the stand alone version of the profile manager in the Mozilla Firefox folder and the new installation of Firefox automagically started working again without need for stand alone profile software intervention.

Until something else quits working I am going to call that good and leave well enough alone.

I don’t like surprises and I don’t like people fiddling with my computer or software without my knowledge. If you feel the same way, you might want to disable automatic updates. That is, disable automatic updates on add-ons as well as Firefox. I assume you have already denied access to Microsoft for their experimentation with updates on your computer.

High power antenna solution for 75 meters

This is not a DX solution. Your best chance of working DX on 75 is to use some sort of vertical because it is costly to build beams for 75 and even more costly to get them to a height where they can be effective.

The system described here would be useful in providing omnidirectional coverage out to as much as 1000 miles to provide effective communications for a net control function on 75 meters.

The feedline is coax with RG8 preferred. Suitable RF choking on the feedline to prevent feedline radiation may be helpful. The antenna requires a mast height of approximately 55 feet to allow an inverted vee configuration with an included angle of 90 degrees between legs.

Each leg of the dipole is 55 feet long and there are two legs per side for a total of four 55 foot legs. The frequency response of the system can be adjusted by varying the distance between the lower ends of each leg pair. Starting distance goal of three feet is good. This installation with a 3 foot distance between lower ends resulted in a 1.5:1 SWR bandwidth from 3.75 to 3.99 mhz. Increasing the distance between leg ends lowers the frequency response while increasing SWR bandwidth somewhat.

The end result is an antenna system for 75 meters that can easily accommodate power levels in excess of 1000 watts while keeping RF levels at the operating position to a minimum.

Yes, this is a cloud burner with a 90 degree take-off angle, but it is one of the more effective cloud burners.

Open Wire Line – Antenna Tuners

For decades I ran open wire (300ohm twin lead) to a non-resonant dipole. Using a Z-Match antenna tuner running 500watts, I was able to use this system on nearly all ham bands.

Recently I upgraded the amp. I got a very capable amp using two 3-500Z tubes running 1200 watts output on 75 meters. The first thing I noticed was the hall light glowing when I tuned up key down.

Shortly after that I replaced the run of 300 ohm twinlead with RG8X to a broadband dipole centered on 75 meters. That made the hall light stop glowing. It also stopprd knocking my computers off the internet and got rid of the radio interferrence.

I guess I am going to have to retire the old tuner if I want to run power. That is okay. I got 20, 15, and 10 covered with a four element beam. Forty meters is covered with an inverted L. Seventy-five meters has the dipole. Thirty meters has a half-square. The other WARC bands have a multiple band moxon. So I really don’t need the tuner or multiband dipole.

Software Defined Radios (SDR)

When Ten Tec came out with the Pegasus I just had to have one. The Pegasus was and early SDR. Still pricey but less than other SDR options. The Pegasus was just an average 100 watt transceiver. The only special thing about it was that it required a computer to make it work. It also contained more than just the average number of relays inside to make it work properly. I don’t much care for relays. I can’t remember when I had a good experience with relays. These cumbersome mechanical contraptions are a constant source of problems.

I soon tired of having to dedicate a computer to the Peagasus. listen to the constna clatter of relays and lack of real knobs to twist had me selling the thing mere months after the purchase.

The radio may be software defined but its performance is still limited by hardware.