Topband: Hairpin Matching Coil Questions

[Tom W8JI]

Hi Jim,

A gamma match is an arm extending out or up on the element from the "ground" 
point. It is named "gamma" because it looks like the capital Greek letter 
called "gamma". See http://en.wikipedia.org/wiki/Gamma

A beta match is called a beta because it extends equally on each side of the 
neutral point, roughly looking like the Greek letter beta on it's side 
http://en.wikipedia.org/wiki/Beta

A hairpin match is a hairpin shaped "stub inductor", generally balanced, but 
it could be unbalanced.  It is called a hairpin because it looks like a 
hairpin, just like a "bobby pin" spread out a little.

A shunt matching component can be used, either an inductor or capacitor, but 
this is typically called shunt matching because it is a shunt component 
across the feedpoint. It is not a hairpin unless it is in the form of a 
hairpin.

Hairpins and shunt matching generally act like L networks, with the series 
reactance in the element (caused by adding or subtracting length to move the 
element away from resonance). Gamma and Beta matchs can do the same, use the 
adjustment in length away from resonance to act like a reactance, or the 
Gamma or Beta might contain a series internal component(s) so the element 
can be resonant.

Q can mean many things. The style or construction of the component usually 
has little bearing on the operating Q of the system, unless you have a 
terrible matching system or component design.

The Q people generally talk about in matching is almost always operating Q. 
Operating Q is generally the ratio of real parts of impedance to imaginary 
parts of impedance, or operating resistance compared to component reactances 
in simple systems. For example a simple parallel tank circuit with a 
reactance of 500 ohms in each component shunted by 5000 ohms has an 
operating Q or loaded Q of ten. The component Q might be 300, or 3 zillion, 
and not affect operating Q significantly.

The Q of components is entirely different than operating Q of a system, and 
is the ratio of reactance to resistance in a component.

Q can also be used to describe bandwidth, but if the component or system is 
more complex than a single resonant L, R, and C the Q defined by bandwidth 
might not be related at all to system operating Q as defined by losses.

When I think about all of that, and your desire for a certain coil conductor 
type for a Q of 80 for a hairpin (that doesn't use a coil by definition of 
being a hairpin), none of it makes much sense to me. The Q of a very simple 
matching system would generally be discussed as a ratio of matching system 
reactance to resistance of the system at that matching point. The Q of a 
component in the matching system would generally be defined as the ratio of 
loss resistance to reactance of that component by itself.

For example, a 200 ohm reactance capacitor of 0.05 ohms loss resistance in 
series with an antenna feedpoint of  50 j200 to cancel reactance and match 
the system would have a component Q of 4000 (200/.05) and an operating Q of 
3.996 (200/50.05). If I put in a capacitor with a reactance of 200 ohms but 
a seres loss resistance of .5 ohms, capacitor Q would be 400. This would 
insigificantly change operating Q to 200/50.5 = 3.96.

This all makes me think you have operating Q confused with component Q.

Are you trying to solve some problem by reading stuff somewhere, and getting 
confused by it??? Maybe some misinformation or misunderstanding is making 
your project needlessly difficult for you to manage?

73,
Tom








> MFJ and Texas Instrument used this type of calculation for antenna Q.
>
> The other attachment is what some other people are using with their
> inverted using the K2AV balun and a Gamma match on bands other than 160M.
> So I thought why not use the same gamma setup on 160M and not the FCP. So
> from what you had said best I DO NOT GO THAT ROUTE.
>
> My antenna system morfed into just using my gamma big coil on 160M.
>
>
> On Sun, Sep 15, 2013 at 9:32 AM, Jim GM <jim.gmforum at gmail.com> wrote:
>
>> Has any one used the MFJ-907 and do what I am trying to do on 160M as a
>> hairpin match?
>>>> From what I have been reading, Q needs to be high but not sure how high
>> and what range.  My 6 inch coil with remote tuner in line with the tap on
>> 160m I am getting around a Q of 80. My 2 inch coil has a Q much lower
>> than that I know cause the set up has a much larger band width on 160M.
>>
>> I have around 30 to 40mh of coil from the tap to ground with both coils.
>> --
>> Jim K9TF
>>
>
>
>
> -- 
> Jim K9TF
> _________________
> Topband Reflector
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2013.0.3408 / Virus Database: 3222/6673 - Release Date: 09/17/13
>