RadioBanter - View Single Post

June 16th 05, 11:27 PM

wrote:
Michael Coslo wrote:
bb wrote:
Mike Coslo wrote:
bb wrote:
Mike Coslo wrote:

Now lets talk about antennas. It isn't likely that we will
have single
antennas at any station, save for the resurrection of the old
general
purpose dipole fed with ladder line, run through a tuner.

Or a random wire fed against ground.

Now there's a heavier than air antenna.

That's one
that olde tyme hammes will recognize! I suppose the Steppir
antennas
could work if you have enough coin. The method proposed by
Jim will not
accommodate the tricks we use now to provide an acceptable
match as the
major HF bands will not be harmonically related.

???

There are solutions to both the rig and antenna problems. But
they aren't as easy as some would have us believe. More important,
unless a considerable number of hams equip themselves to use the
new bands, they aren't much help.

The American Red Cross and County EMA agencies have funded equipment
upgrades in the past. Do you think they'll stop if we get more bands?

And does propagation varies that much between most of the bands we have
now? I don't think so.

Then what was your purpose in putting up such a strawman?

And all agencies that rely upon HF communications would be pleased as
punch to have bands that are separated by 5 megs?

It was argued that the difference in propagation between 80 and 40
could be great enough that access to a band near 60 was needed.
And we almost got a full band there, except that NTIA reversed its
support after 9/11.

But the jump from 80 to 40 is a doubling of frequency. From 40 to 20 is
a doubling also, but we have 30 meters in between. Would a band at,
say, 8.5 MHz be that much different from 7 and 10 MHz?
Or would we be better off with more worldwide-exclusive-amateur-kHz on
40 and 30?

Lots of questions.

Before you start in on your "what if's," what is your intended purpose?

Purpose should direct repsonse.

Trap dipoles don't have to be on bands that are harmonically related.

I've built and used trap dipoles. The more bands you add, the more
complex the adjustment procedure becomes.

Does anyone else here have experience building trap dipoles from
scratch?

Cushcraft handles it nicely by having a trapped antenna for the
20/15/10 meter bands, and another for the 17/12 meter bands. I think
each antenna has an optional trap for 40 and 30M.

The random wire antenna you suggested is doable, and the low dipole is
a good NVIS performer.

Perhaps we should go back to what Jim posted with his original question:

Jim's quote
* Right now we have 9 HF/MF bands, plus some spot frequencies in
* the "60 meter" region.
*
* Suppose that at some point we hams had the choice of either:
*
* 1) New, very narrow bands elsewhere in the HF/MF spectrum (say, 2.5 to
* 2.6 MHz, 6.0 to 6.1 MHz, etc..
*
* or
*
* 2) Widening of existing bands and/or change to worldwide amateur. Such
* as 7.0-7.4 becomes worldwide exclusive amateur, 10.1 to 10.2 does the
* same, 14.0 to 14.4 (which the band used to be), etc.
*
* Which would be preferable, if we wound up with the same number of kHz
* overall?

End Jim's quote.

Under Jim's scenario, we would be adding several bands.

Under one of my scenarios, anyway.

That trap dipole would be interesting indeed! Likely mostly traps.
Maybe I'll try to design one. Jim will have to give me the specific
frequencies that will be added in his scenario.

Let's say the following additions/changes were made:

A new band 50 kHz wide at 2.7 MHz
A new band 50 kHz wide at 8.6 MHz
A new band 50 kHz wide at 11.9 MHz
A new band 50 kHz wide at 16.0 MHz
A new band 50 kHz wide at 19.6 MHz
A new band 50 kHz wide at 23.2 MHz
A new band 50 kHz wide at 26.4 MHz

or

5.1 to 5.2 MHz instead of 5 channels
7.0 to 7.3 worldwide exclusive amatuer
10.1 to 10.2 worldwide exclusive amateur
18.05 to 18.2 worldwide exclusive amateur

Fine. Why do we need any of those bands? State your purpose and we'll
consider suitability.

And trsp dipoles are not a very universal answer. In my
situation I
would have to make a loaded trapped dipole for 80 meters and to cover
other bands. Now *that* would be a hoot! And quite heavy.

Some folks can't even get a random wire up and radiating HF RF....

Usually radiates via the mic/key cable.