Still Tweaking...

erobertg · Post by **erobertg** » Sun Jan 02, 2005 12:55 am

The weather hasn't been too cooperative but I did try an experiment by putting different capacitors between the lower ground plate and the mast. The lowest SWR was about 2.2:1. Range is good but I'm going to try a few more ideas.

Inductive loading coil...Interesting.

Antler · Post by **Antler** » Tue Jan 04, 2005 2:33 am

This is depressing.....

Reference antenna performance, I have been checking out some of the mobile antenna sites and have found some interesting stats on some on antennas for 160 meters. One antenna cut for 160 meter band boast 1.3 percent efficiency (others are much worse).

Think about it, 10 watts into the "Hi Q mobile" antenna yeilds a whopping 130 milliwatts ERP. (effective radiated output)

I am starting to think very tall... as tall as I can make it without a tower. That will probably be 45 or 50 feet up through the middle of a tree.

Here is a link to a page with some more ideas: http://www.cebik.com/fdim/fdim8.html

erobertg · Post by **erobertg** » Tue Jan 04, 2005 3:45 am

An interesting article...

One thing that should be noted is the Isotron has both a capacitance hat (1.3 sq. ft.) on top and a ground plate on the bottom the same size. It's not just a loaded whip which tend to be very inefficient.

Antler · Post by **Antler** » Tue Jan 04, 2005 4:08 am

Yeah, I am not sure how much of this theory applies to Isotron. It sounds like the Isotron is working for you though and that is great..

From what I am reading, it is not easy to make an efficient antenna that will radiate on the lower frequencies. So, since I love to tinker with antennas, I am looking forward to trying out a few designs to see if I can get something to work really well.

erobertg · Post by **erobertg** » Wed Jan 05, 2005 1:46 am

If you are intent on trying experimental designs, have you considered a helically wound antenna? An 8-10 ft/ 4" PVC pipe wound with 14 awg wire and using a aluminum pie plate or larger for a hat.

A program called HELICAL3.EXE can be found with your search engine and will calculate even efficiency.

Antler · Post by **Antler** » Wed Jan 05, 2005 2:37 am

I have not really planned to try a helical as I really don't know of any successful examples of one that is in use on the low bands that works well. I have seen several comercial antennas built on this model and the only good comments I hear are from the manufacturers.

I will ask the expert though to see what he thinks it. I am always ready to learn something new.

Thanks for the suggestion.

Antler · Post by **Antler** » Fri Jan 07, 2005 2:55 pm

On helicals, I did get in touch with my antenna Guru yesterday and we did briefly talk about helicals. He said he was familiar as he had done a research paper on them while getting his masters. His conclusion was much the same as mine in that he said the helical wasn't very efficient on this band.

He did have an idea for a legal part 15 antenna that has some gain and should be very effective. More on this subject later....

BTW, I think I got some old juices flowing for him with our conversation on antennas as he said he would build the antenna for me. (That is great for me as I have little or no time)

I can't wait.

PS. Our conversation started like this... "Well, the impedance of free space is 377 ohms....."

Antler · Post by **Antler** » Fri Jan 14, 2005 3:24 am

I received my transmitter today.... The transmitter seems to sound pretty good as long as I don't overdrive the audio.

Anyone have the prefered setting on DSP? I tried the settings shown in the pictures from the manual thinking they might be the suggested settings.

Post by **pcs** » Fri Jan 14, 2005 10:33 am

Increase compression ratio to 8:1
and lower threshold to -24dB or so.

erobertg · Post by **erobertg** » Fri Jan 14, 2005 2:44 pm

That's funny, my compression threshold only goes -15.0 dB max.

Post by **pcs** » Fri Jan 14, 2005 6:41 pm

In latest model we increased this to 24 max i think.

Do you want an update chip?

erobertg · Post by **erobertg** » Sat Jan 15, 2005 3:06 am

How much$? What am I going buy, I bought the AM transmitter in November 2004. To tell you the truth, the modulation is fine at -15dB but what does going down to -24 dB do?

I might be interested in the new 100 watt AM transmitter.

Post by **pcs** » Sat Jan 15, 2005 11:53 am

I think its wise to wait for the new version,
this update makes almost no difference to you.

What id does; it makes compressor/limiter more agressive,
the chip plus shipping is about 25 euro.

Antler · Post by **Antler** » Thu Jan 20, 2005 4:07 am

Random thoughts and Questions ???

I received my transmitter and haven't really used it yet except to hook it to a dummy load via a watt meter and listened to it around the house. (I am waiting till I get my antenna built before give it a try)

Marko, Just in case I want to try it out before I get my antenna up, does the transmitter have a roll back circuit for protection of the finals with high SWR?

"erobertg" I just finished reading the manual on the Isotron and I was suprised to see that the infamous picture of what it looks like is not what it always looks like when you get finished building and tunning it. How much of tuning paraphernalia did you wind up using and how low is your SWR? Is your good usable range still around two miles or is it improved since you last reported?

I called my brother in law and he hasn't started the EH antenna yet. Here is a picture of what one looks like. I hope he gets started soon so I don't have to do it myself. Anyone need a job?

BTW, my wattmeter shows 18 to 20 watts into a dummy load. It bounces a little higher while being modulated... Maybe my wattmeter is inaccurate at this frequency? On another note, I am interfering with the telephones I hope I am not causing Television interferance, that will get me busted in a hurry. Anyone else have problems with interferience?

A-man

Post by **pcs** » Thu Jan 20, 2005 9:53 am

There is no SWR protection.

AM causes this kind of interference by radiation, you need
to take common steps to avoid it, like moving antenna away
from equipment, RF blocking everything etc.

Remember, this can't be fixed by filtering. Cheap electronics
equipment has no RF filtering and will readily demodulate any
strong AM modulated RF signal regardless of the frequency.

This happens in the audio stages of your phone/tv, casette
player, cd player etc usually.

erobertg · Post by **erobertg** » Thu Jan 20, 2005 3:38 pm

I see that your interested in the EH antenna...A revolutionary concept.

I got of splash into telephones and audio when I used a random length wire and tuner. With the Isotron I just get usually AM harmonics for about 50-100' feet. Normal cross modulation on the AM dial just around the house and not beyond which is normal close antenna conditions.

I got my max range with a Subaru car radio (6-8 miles). For the first mile my signal is as strong as any local station. The second mile can be picked up clearly on any radio and mile three comes in very good on my car radio. Remember, your dealing with about 10 watts, not 1,000, or 5,000 or even 50,000 which. A 1,000 watt station theorectically has 100 times the power which means it should go 10 times as far (inverse square law.) Just get on a very clear frequency which will be able to be picked up by sensitive receivers.

About SWR, it can vary between 1.7 to 2.4 depending on snow, ice accumulation and temperature swings. I'm always putting out at least 80% power.

erobertg · Post by **erobertg** » Thu Jan 20, 2005 4:14 pm

Soil conductivity plays a role in AM range because of ground wave. New England has poor conductivity but other areas are much better. Your frequency plays some role too (540-1700 kHz.)

http://www.fcc.gov/mb/audio/73184/index.html

Lower frequencies will propagate futher. If you transmit near the coast near salt water will give you 10 times the range or more.

Antler · Post by **Antler** » Fri Jan 21, 2005 2:14 am

I got my max range with a Subaru car radio (6-8 miles). For the first mile my signal is as strong as any local station. The second mile can be picked up clearly on any radio and mile three comes in very good on my car radio. Remember, your dealing with about 10 watts, not 1,000, or 5,000 or even 50,000 which. A 1,000 watt station theorectically has 100 times the power which means it should go 10 times as far (inverse square law.) Just get on a very clear frequency which will be able to be picked up by sensitive receivers.

Cool, thanks for the details and the link. That gives me an idea of what I am looking at. I wonder how far a typical transistor radio would pick it up? Guess I will find out.....

Thanks,

A-Man

erobertg · Post by **erobertg** » Fri Jan 21, 2005 2:23 am

That logo...I worked at East Hartford and later at Middletown.

Antler · Post by **Antler** » Fri Jan 21, 2005 2:36 am

I never worked for Pratt but I am a big fan of P&W products. Pratt products have been some of the most reliable products on the market. My experience with Pratt mainly includes the JT8D but I have several thousand hours of R985 time as well back in my formitive years.

Today, I am using Rolls and GE products ....

A-Man

PCS-Electronics

Still Tweaking...

Still Tweaking...

Antenna Design...

Helically Wound Antennas...

How Much?

EH Antenna...

By The Way...

Antler...Did you work at Pratt?