KB4QAA provides sound advice on how to 'tune' your dipole.

An attic can be one of the worst environments for an amateur radio antenna.  Why?  Basically significant and often quite detrimental interactions with the nearby structures of the house and specifically with electrical house wiring, ventilation ducts, home security (smoke detectors) wiring, outdoor metal gutters and downspouts, etc.  These interactions play havoc with SWR, element balance, radiation pattern; e.g., especially when one section of the antenna is sitting within a few meters of the A/C unit or runs parallel to your metal gutters.

For this environment, I would definitely recommend the use of their balun.  Get some decent coax also - you need all the help you can get and something like LMR400 provides added shielding.

Hy-Power Antennas make quality products: excellent materials, good design.  Most products can work 'straight-out-of-box' where one doesn't even need a tuner.  But because they use loading coils there is a sacrifice in bandwidth and there are losses associated with the coils themselves.  (I personally would like to see them add optional 'low loss coil/higher Q' coils) Your particular installation should work once you get it tuned for the frequencies where you want to operate.

GL, 73, Rich, K3VAT
(no connection to Hy-Power Antennas)

That may be so, but Amateur Television is on the exams [Ex. S 8.2] and there are probably way fewer TV'ers than DX'ers. 


What survey did this come from? 

This is pretty much my take on this.  Besides the lids calling on frequency there is the 'tuner-uppers' and for me these may even be more malicious and disruptive.  If the 'calling on frequency' and the 'tuner-uppers' were not there, then their would be no cops - simple - the cops are often the 2nd layer of frustrated operators (the continuous callers are the first).

Perhaps all amateur radio examinations should incorporate a section called "DX operating guidelines" and have a pool of a dozen questions that address, among other things, this exact topic - probably wishful thinking.  As was pointed out several times in this thread, it is an education issue.

73, Rich, K3VAT

Jim,

Here's one link with tons of information that is a must-read for coil builders.  Keep scrolling down for more and more goodies about the theory of coil inductance, building techniques, links, etc.

http://hamwaves.com/antennas/inductance.html

For specific answers to you questions, it would be helpful for us to know what you have in mind as far as the antenna such as the band of operation, power, antenna system characteristics, etc.  May be this is for a wire antenna hung between supports as you'd like light weight.

Perhaps 1.5mm winding wire isn't the best approach; coil factor typology, wire spacing, # of turns are important and should be optimized based on the above.

GL, 73, Rich, K3VAT

*composed the same time as the previous posting *


Capacity hats, whether employed in a monopole vertical or at the ends of a doublet do in fact radiate.  Anytime one has current flowing through the hat components you're generating a flux field and hence radiation.  The key is one needs to design and build the hat(s) so that the antenna system is balanced: currents in one side of the radiator's cap hat swing positive, the corresponding other side swinging negative (with the same magnitude absolute value).  So the net effect, radiation-wise, is that in the far field the radiation vectors are nullified.  The resultant radiation is then determined by the topological configuration of the main radiator element and by other factors such as height above ground (as for a horizontally polarized dipole).

To function properly, cap hats don't need to be at right angles to their main radiator element.  They can be angled.  Please see ON4UN LowBand DX'ing Text, section 3.6.2 of chapter Nine.  There are diagrams to help in the visualization.  The key here is that both sides of the cap hat wire have the same vertex angle.

GL, 73, Rich, K3VAT

A few questions:
(I'm assuming both radios are similar, e.g. HF transceivers)
1. how much power do you intend to run (the answer will help determine which switching device(s) that you need)?
2. what is the distance between the rooms; are they on the same or different floors?
3. will both radios need both transmit and receive switching?

There is equipment that can easily do this.  Start by checking out arraysolutions.com (for the high-end products) and this

http://www.eham.net/reviews/products/2

GL, 73, Rich, K3VAT

The factory defaults are only one approximation.  Your setup is unique, so you'll need to:
1. tell the controller that you have the 80M coil (appears that you have done this)
2. in "create modify" use a combination of the "coarse up/down" and the "fine up/down" to tune your antenna.

After modification, if the SWRs are NOT nominal, then you'll have a concern.

GL, 73, Rich, K3VAT

Thank you for your posting.  However, I'm having trouble with the calculation in your last paragraph, and would like some assistance.

For a 70 degree H shortened vertical I examined the graphic (from your link) for 60 radials and from the chart is appears that when using .2 wavelength long radials the percent loss in the ground system equals ~ 26%, correct?  When using .4 wavelength long radials the percent loss in the ground system ~ 11%, correct?  Doesn’t that equate that the .2 wavelength long radial system has a little over twice the associated loss when compared to the .4 wavelength long radial system?

A 70% vertical has a radiation resistance ~ 22 ohms, per figure 9-7 from ON4UN’s text (page 9-5).

If we assign a 5 ohm loss to the shortened vertical described by Smith for the system using .4 wavelength long radials, and using a RR = 22 ohms, the antenna system efficiency is then 22/(22+5) or about 81%.  If we then use a 11 ohm loss (this is a bit more than twice the loss calculated from above) for the system using .2 wavelength long radials, the system efficiency is then 22/(22+11) or about 67%.

Comparing the efficiencies of these two systems: 81% vs 67%, it appears that the using .2 wavelength long radials drops system efficiency only about 20%, correct?

Assigning higher loss to the above, say a loss of 10 ohms for the system using .4 wavelength long radials, then the ~ loss for the .2 wavelength long system equals approx. 22 ohms.  Using the same efficiency formula, the .4 system ~ 70% and the .2 system exactly = 50% efficiency.  The drop in system efficiency for this example (70% vs 50%) is more pronounced at ~ nearly 30%, correct?

These calculations seem to be markedly different from those appearing in your posting (last 2 sentences).

73, Rich, K3VAT

I've had my K3 for 2 years now.  I also have the KPA500 and KAT500, and no second RX in the K3.  What I do have is a LP-Pan Adapter with big 27" high res monitor.  For me personally, this is the equalizer as I like seeing the split, whose working the DX and any pattern that the DX is using to answer the callers.  When I got the K3, I thought that I'd get a 2nd RX a bit later, but now I don't really need it.  73, Rich, K3VAT

KR4TH: K0ZN summaries the issues nicely.  For more detailed discussions you can search the forum archives - there is dozens of postings and hundreds of comments on this popular subject.

GL, 73, Rich, K3VAT

I've successfully used this type product for winding a loading coil on a 4" diameter form.  You can search for similar size and lengths of soft aluminum wire or tubing.  Small tubing (0.25") may provide both the workability you want while providing lower resistance (compared to #12 Al wire), plus no worries on dissimilar metal connections.  Some solid copper wire, like those 25' rolls of 'grounding wire' that are sold by Lowes and HomeDepot (anywhere from #4 up to #10) are often hard to work with, especially when trying to wind a uniform coil while maintaining coil spacing.

http://www.etsy.com/listing/115278048/6-ga-aluminum-wire-5-ft-coil-soft-pure?ref=similar_items_sash

GL, 73, Rich, K3VAT

My choice same as above.  PT0S crew was really heroic!  73, Rich, K3VAT

I agree with K2DC on this - don't see any real evidence that you'll gain anything over what you already have.
You might consider enhancing the 6BTV by increasing the number/length of radials (your minimum should be around 30) and/or raising the height of the OCFD.  Didn't notice what your operating goals are: working the 'locals', occasional DX'ing, or perhaps all-out DX'ing; working into a specific region; etc.

GL, 73, Rich, K3VAT

Most likely. You're planning to place the proposed vee right in the center of the near-field with each leg of the vee a harmonic of the vertical.  When using the vertical, you'll have max voltage at the top of the vertical, right where the vee attaches.  They will interact - how much depends on a number of factors, but like K2DC correctly pointed out "... you'll never know ... until you try it ..."  AND "... unless you intend to drop the vee while using the vertical."

The same principle holds for guying towers.  You break up (or cut to specific lengths) each guy wire by using insulators to prevent the guys from interacting with the antenna's signal.

GL, 73, Rich, K3VAT

Ah, a vertical dipole - nice construction.  You seem to have identified all the necessary components (loading coil and cap hat, one for each side; and shunt coil at the feedpoint.  Thanks for sharing.  73, Rich, K3VAT