[TowerTalk] 6M yagi above a tribander

[Grant Saviers]

My experience with a DB36 and 80 shorty dipole cause me to believe that 
linear loaded yagis can be significantly affected by other antennas on 
the same mast.  My dipole was both element aligned and boom aligned at 
11 ft separation and significantly disturbed the DB36 on 30 and 40m.  20 
 > 6 there is very little interaction.

Off course every antenna combination will be different.  JK antennas 
advertises for a couple models that they are not sensitive to others. 
Modeling is a way to get an answer, more difficult with trapped antennas 
when the trap models might be hard to find.  Then the question is what 
interaction and how much of it (G, F/R, F/S, SWR) is acceptable?  My 
modeling experience is that a good swr doesn't tell you much about the 
other three, but a bad swr means something is amiss in them.

Some no/low interaction counter examples also exist - my 4L steppir with 
add on 6m elements on the same boom.  Because of almost 2x the height 
for my 4L, with the add ons, performs essentially as well as a 6m M2 
6M5XHP 5 over 5 stack at 38/53ft. So with some hard work and luck re 
where elements can be placed it is conceivable a 6m 5 element could be 
interlaced on a TH11. Separate feedlines make such designs easier.  The 
3 and 5 band no trap interlaced beams are awesome engineering works of 
art IMO, having tried modeling of a couple of them I'd like to build.

Also, the more separation likely the lower the interaction.  The VHF 
literature has much to say about stacking re capture area.  As a 
practical matter, plot the swr for each HF band before and after putting 
up the 6m. Then worry or not.  The wind load from either is low so your 
tower may allow a mast extension.

Grant KZ1W

On 1/8/2022 07:27, mike stokes wrote:
> I have the same question except that I want to use a 5 Ele 6 and a TH11.
> 
> I appreciate thoughts for both Pete and my questions.
> 
> 73
> Mike
> KK9V
> 
> On Sat, Jan 8, 2022 at 10:09 AM Pete Smith N4ZR <pete.n4zr at gmail.com> wrote:
> 
>> I have just bought a 3-element 6-meter yagi (Cushcraft), and plan to
>> mount it above a C-3E tribander.  Would a quarter wave spacing above the
>> tribander be sufficient (5 feet), or do I need more?  I'll likely just
>> have one convenient shot at this when I have the rocket launcher down
>> this spring, and I'd like to get it right from the start
>>
>> --
>> 73, Pete N4ZR
>> Check out the new Reverse Beacon Network
>> web server at<http://beta.reversebeacon.net>.
>> For spots, please use your favorite
>> "retail" DX cluster.
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
> 
>