options for 10m? Tarheel 200a, cap hat, 1ft mast, 70" whip

[mr_fx]

Right now I am running the Tarheel 200a with the 1 ft extension, the (tarheel) cap hat (20" spoked), and a 70" whip (I have ordered the Scorpion cap hat with 3 foot extension,.... it is quite a deal for only $100.00 shipped)

The big problem I have ran into is that since the antenna is far too tall for 10m work I have to run the coil several turns down to get a match, and it is a bit of a dummy load on 10m as a result

This is about what I am running now (these are the readings from the Ameritron SDC-102 display)

20m = about 46 turns
40m = about 145 turn

10m = about 345 turns

80m = about 450 turns(plus or minus about 20 or 30 turns)

I am really weak on 10m... much weaker than I expected the antenna o be even though it is to big for 10m

I am considering a 10m nmo mount on the roof, but I am open to all sorts of ideas

I knew that it would be down on 10m, I just did not think it would be as weak sauce as it is

 

[w9cll]

Right now I am running the Tarheel 200a with the 1 ft extension, the (tarheel) cap hat (20" spoked), and a 70" whip (I have ordered the Scorpion cap hat with 3 foot extension,.... it is quite a deal for only $100.00 shipped)

The big problem I have ran into is that since the antenna is far too tall for 10m work I have to run the coil several turns down to get a match, and it is a bit of a dummy load on 10m as a result

This is about what I am running now (these are the readings from the Ameritron SDC-102 display)

20m = about 46 turns
40m = about 145 turn

10m = about 345 turns

80m = about 450 turns(plus or minus about 20 or 30 turns)

I am really weak on 10m... much weaker than I expected the antenna o be even though it is to big for 10m

I am considering a 10m nmo mount on the roof, but I am open to all sorts of ideas

I knew that it would be down on 10m, I just did not think it would be as weak sauce as it is

Put a shorter whip on it maybe. I run a High Sierra sidekick and I can easily tune 10 and have worked all, I can even tune 6 meters with the 72" whip installed.

 

[W5LZ]

I'm not sure how those 'turns' are figured/given. It they are the number 'exposed' then that 10 meter setting is off by a huge amount. I would think only a couple of turns would be exposed not almost as many as for 80 meters.
Just for grins. If your present tophat isn't above the coil by a foot or two, you'd be better off removing it.
- 'Doc

 

[mr_fx]

ok with the antenna fully collapsed it tunes around 21MHz but I knew this would happen

my hope was that the performance hit on 10m would be minimal... I also figured the 10m 2nd tap would be closer to 200-250 turns


BTW the turns are rotations of the stepper motor in the antenna... when the turns read '0' the antenna is fully collapsed, the antenna is fully extended around 990 turns

the plan was to assemble a really good performing 80m-15m mobile while taking a small hit on 10m... but it turns out it is a massive hit

 

[W5LZ]

Shorten the whip. The thing fully collapsed is the highest band of use. Fully extended is the lowest band of use. If the highest is 15 meters, shortening the whip would get you to 10 meters, right? I figure there should still be enough 'coil' there to get back down to 80 meters. Try it and see...
- 'Doc

 

[w9cll]

Shorten the whip.

Hey thats what I said

 

[mr_fx]

I could remove the cap hat... or the whip... either would get me 80-10

BUT then I take a hit on 80-15

 

[W5LZ]

I don't think you'd be taking a 'hit' at all. You aren't using half the available 'coil' now so you could still reach 80 meters.

'CLL' - yep, same thing just in a different way. Sometimes that's all it takes, right?

 

[M0GVZ]

Once you get > 1/4 wave electrically on a frequency, higher angle lobes appear and increase in strength as the antenna gets longer getting to the point they have more strength than lower lobes and you start to get sharp nulls as well.

 

[M0GVZ]

I'm not sure how those 'turns' are figured/given. It they are the number 'exposed' then that 10 meter setting is off by a huge amount. I would think only a couple of turns would be exposed not almost as many as for 80 meters.
Just for grins. If your present tophat isn't above the coil by a foot or two, you'd be better off removing it.
- 'Doc

They're not configured in any manner. The antenna doesn't have an internal turns counter, it is literally a switch that is turned on with every rotation of the motor. The Ameritron literally counts the number of turns the motor makes. It bears no linear resemblence to the amount of coil that is exposed which is why such controllers are a bit of a pain in the ass and regularly need recalibrating.

 

[M0GVZ]

I don't think you'd be taking a 'hit' at all.

Performance wise he will. I have a Little Tarheel II and doubling the length of the stock whip made a massive difference, effectively as much as running a linear amp.

 

[W5LZ]

I'm not familiar with the Tarheel or MFJ's turns counter. I do have a screwdriver antenna and use the number of exposed coils as an indicator. That's why I tend to relate a 'counter' as counting coil turns.
I agree about there being a possible gain in performance depending on the 'length' of the antenna, that's absolutely normal when dealing with any loaded antenna. The closer you can get to a full 1/4 wave length the better off you are. For the higher HF bands it's 'possible', just not too likely below something on the order of 12 meters or so. The thing would be too long to comfortably drive around with. That's also why making a fully collapsed screwdriver the height of a 1/4 wave on the highest band of interest is a good idea. That's what I was trying to get across. Once you start loading a short antenna, the more you load it the less performance you will get. Once down to around 80 meters you will be very lucky to get 2 or 3% efficiency out of any mobile antenna. But, I think we've both seen/heard 80 meter mobiles that do quite well at 2 or 3% efficiency, right?
Oh well.
- 'Doc

 

[w9cll]

Performance wise he will. I have a Little Tarheel II and doubling the length of the stock whip made a massive difference, effectively as much as running a linear amp.

I will confirm this as well, with my High Sierra the stock whip was 36" and tuned 6-80. I replaced the whip with a 72" and it made a huge difference on 20-80 but at the cost of the high side of 6.

 

[mr_fx]

I don't think you'd be taking a 'hit' at all. You aren't using half the available 'coil' now so you could still reach 80 meters.

'CLL' - yep, same thing just in a different way. Sometimes that's all it takes, right?

I am quite aware of this, but having less physical size on 80 and 40 WILL mean I take a hit there, and even a hit on 20 and 15 though to a lesser degree

I tired 10m on the antenna and it did not work ou... but I knew this was likely before I even got started... so oh well

 

[mr_fx]

Performance wise he will. I have a Little Tarheel II and doubling the length of the stock whip made a massive difference, effectively as much as running a linear amp.

Thank you!

would you be interested in a tarheel cap hat that is only a few weeks old?