Register Account

Login Help


Joined: Tue, Nov 28th 2000, 00:00 Roles: N/A Moderates: N/A

Latest Posts

Topic Author Posted On
43' verticals -- what's the theoretical basis? KE2IV on 20/10/11
Quote by SIZE358
the 43 foot vertical is 5/8 wave on 20m and is 1/4 wave on 60m.

That doesn't have anything to do with 160, 80, 40, 30, 17, 15, 12, and ten meters. :-)

My guess is someone took the 88 foot doublet and turned it into a Marconi. But that's just a guess.

Whatever it is, a trap vertical like a 6BTV will work a whole lot better.
43' verticals -- what's the theoretical basis? KE2IV on 12/10/11
Quote by KE2IV
QST is filled with ads from various manufacturers and suppliers offering "all-band" 43-foot verticals. Legitimately, all these ads make it clear that this (and any vertical) will require a good ground plane system of radials for effectiveness.

But why 43-feet? What is the "formula" to explain why this length will effectively radiate on "all bands" (i.e. 160m - 10m) with a decent ground plane system?KE2IV

There is no reason, George. Somehow that number just popped up out of the blue, and then everyone started copying it.

The initial 43 foot vertical had a balun that, through an error in design, drove the coax shield with RF. This error, in some cases, made the SWR very low from 160-10 meters. Hence the "160-10" meter stuff started.

After an eHam thread, the company initially marketing the 43 foot vertical revised the voltage balun to an un-un, and then the SWR was not so good at all but the signal was better.

To radiate 100 watts of actual field power on 160 meters with a 43 foot vertical, the base voltage would be 6500 volts peak at 6.6 amperes!! On 80 meters, it would be 1200 volts peak at 3.2 amperes.

At 500 watts actual radiated power on 160 meters, a 43 foot vertical will blow the insulators apart.

The 43 foot vertical mainly "works" because of power losses in the matching and feed system. They are OK on 60-15 meters, but not especially good anywhere.

If you want a good 80-10 meter vertical, buy a trap vertical. DX Engineering sells Hustler verticals that are OK on 80 (but narrow banded) and great from 40 meters up. HyGain sells a Hytower, that while pricy works excellent from 80-10 and can be loaded to work 160.

When you buy a simple antenna with no band-by-band matching, either through complex tuners, traps, or stubs, matching, you can bet it is throwing power away someplace.

The better SWR it offers in less space with less complexity, the power it throws away. There is no free lunch, George.

Here's a final thought. I know of several very high rated antennas in Internet reviews, one is a 5.0 out of 5 on eHam, that have less than 10% efficiency on many bands.

Anything that makes a QSO and has a low SWR works perfect to some people, even if 95% or more of their power is wasted as heat.

73 Tom
What rigs do you use for AM operation and why do you like using AM? W1RFIAdmin on 12/10/11
Quote by K4TOJ
Here's a question about something I've noticed while looking at transceivers. I have a Kenwood TS-930S which will transmit 100W in all modes including AM. Most of the current rigs may transmit 100W in all modes but AM. For some reason, they limit AM to 25W, 40W or 50W max. So the question I have is why is this? Do they limit AM because they don't make the finals like they used to?

Your TS930 will not run 100 watts of AM.

If you read the manual, the carrier power is supposed to be adjusted to 15-20 watts carrier OUTPUT power.

Older rigs were rated in input power. Your Kenwood is rated 80 watts AM input power, and 15-20 watts carrier output power.

Nearly all AM rigs, at least for Ham use, were a combination of screen and plate modulation. About 60-80% of the modulation power came from the modulator stage, with the remainder of modulation power from the screen of the PA tube. It was a combination of efficiency and plate modulation.

Older rigs like my Ranger were 65 watts AM input power. That was about 30 watts carrier power. Remember everything prior to 1982-83 was rated in plate input power. A 2KW Heathkit SB-220 amplifier is rated at about 600 watts CW output, and around 1100 watts SSB PEP output.

Those old rigs were not as big as the advertised power makes them appear because of the change from inoput power to output power in the early 1980's.

73 Tom
Water near boat as a counterpoise? KE7UGT on 29/9/11
It is a counterpoise, but a very poor poor one, unless it is salt water. Fresh water has worse conductivity than good dirt.
Low Pass Filter installation HF K1SND on 27/9/11
A low pass filter is almost a thing of the past. They had value with old tube radios, but most solid state stuff is very well filtered and shielded.

Also, very few TV systems are on antennas and none of them have low TV channels any longer.

I can't imagine why you would want an LPF, but if you do it should go right on the output port of the PW1.

Back to Top


Instragram     Facebook     Twitter     YouTube     LinkedIn