[Repeater-Builder] Re: Two Repeaters, One Antenna

[ldgelectronics]

That's not much information. Please explain how that would be used.

Dwayne Kincaid
WD8OYG


--- In Repeater-Builder@yahoogroups.com, Jay Urish <[EMAIL PROTECTED]> wrote:
>
> This is where you use a combiner...
> 
> 
> 

[Repeater-Builder] Re: Two Repeaters, One Antenna

[ldgelectronics]

I know exactly what a hybrid combiner is (have several in use). I'm 
more curious to see how you propose to use that type of device to 
solve the problem that has been presented.

Dwayne Kincaid
WD8OYG

> When I talk combiner, think duplexer on steriods..
> 
> Do a google search on hybrid combiner..
> 
> A combiner with give you several rx and tx ports..
> 
> ldgelectronics wrote:
> > 
> > 
> > That's not much information. Please explain how that would be 
used.
> > 
> > Dwayne Kincaid
> > WD8OYG
> > 
> > --- In Repeater-Builder@yahoogroups.com 
> > , Jay Urish  
wrote:
> >  >
> >  > This is where you use a combiner...
> >  >
> >  >
> >  >
> > 
> > 
> 
> -- 
> Jay Urish W5GMex. KB5VPS
> 
> ARRL Life Member  Denton County ARRL VEC
> N5ERS VP/Trustee  
> 
> Monitoring 444.850 PL-88.5 146.92 PL-110.9
>

[Repeater-Builder] Re: Two Repeaters, One Antenna

[skipp025]

Seen and done this before... 

Two Motorola T-1500 type duplexers, one setup on each repeater 
along with the proper tx circulator for each. The antenna port of 
both duplexers joined with another coax T... if you want to be 
really on the money use a n-way and remove the two duplexer 
output T's. 

If the reflected power on the antennas is minimal the system 
should play just fine. I've seen it done at more than one commercial 
repeater site. The frequencies are far enough from each other 
that everything should play just fine. 

cheers, 
s. 

> Cort Buffington <[EMAIL PROTECTED]> wrote:
>
> Guys,
> 
> I've found a site for my most recent Ham repeater project. Nice farm  
> tower on a hill, clean of RF colo, etc. The farm repeater is a 463.xxx 
> + machine and I'm on 444.825. It is set up with nice hardline and a 16  
> bay folded dipole antenna (not sure the mfg., but he thinks it's DB).  
> Anyway, assuming that thing has useable SWR on my TX frequency (I've  
> had that happen before, not holding my breath), does anyone have any  
> ideas about the viability of running both repeaters on the same  
> antenna but connecting the duplexer outputs together in to the common  
> feedline? I've done no math, and not a lot of thinking, but is this  
> one of those times when I might run odd multiples of 1/4 wave coax to  
> a T at the hardline or something? Both repeaters have BpBr duplexers  
> and both have isolators on their outputs.
> 
> 73 DE N0MJS
> 
> --
> Cort Buffington
> H: +1-785-838-3034
> M: +1-785-865-7206
>

[Repeater-Builder] Re: Two Repeaters, One Antenna

[skipp025]

Unless you want to spend time with the proper test equipment, it 
is probably a lot more prudent to make all the cavities in your 
mini antenna system the same or very similar types. 

The stacked T-1500 duplexer layout I describe has the antenna 
ports joined with another T... while this works fairly well one 
could probably do better by coupling each of the series cavities 
into an N-Way ... aka star.  

You could combine duplexers with n-multiple lengths of coax or 
hard line but every extra section(s) is loss, bandwidth restrictive 
and another impedance bump I'd rather do without. 

Two back to back T-1500 duplexers are pretty much the same layout 
as the factory supplied Microwave Associates unit at x-times the 
cost. 

If you want to be uniform... find another T-1500 off ebay cheap 
enough. 

cheers, 
s. 

(ps: What's an N-Way... oh about 4 pounds... :-) 

old bad joke... sorry. 



> Cort Buffington <[EMAIL PROTECTED]> wrote:
> T-1500 type is what's in the commercial repeater (micor). 
> My repeater  
> has a Wacom WP-678-R2 on it.
> 
> Odd multiples of 1/4 coax between duplexer tees and the antenna tee?
> 
> BTW: A big thanks to Skipp, Phil and the rest who've jumped in here  
> today. I sometimes get some crazy notions (ham guy, not commercial 2- 
> way shop here) and I really appreciate this group. I lurk a lot and  
> learn a lot -- only hope I can give back more someday.
> 
> 73 DE N0MJS
> 
> On Feb 20, 2008, at 5:08 PM, skipp025 wrote:
> 
> >
> > Seen and done this before...
> >
> > Two Motorola T-1500 type duplexers, one setup on each repeater
> > along with the proper tx circulator for each. The antenna port of
> > both duplexers joined with another coax T... if you want to be
> > really on the money use a n-way and remove the two duplexer
> > output T's.
> >
> > If the reflected power on the antennas is minimal the system
> > should play just fine. I've seen it done at more than one commercial
> > repeater site. The frequencies are far enough from each other
> > that everything should play just fine.
> >
> > cheers,
> > s.
> >
> > > Cort Buffington  wrote:
> > >
> > > Guys,
> > >
> > > I've found a site for my most recent Ham repeater project. Nice farm
> > > tower on a hill, clean of RF colo, etc. The farm repeater is a  
> > 463.xxx
> > > + machine and I'm on 444.825. It is set up with nice hardline and  
> > a 16
> > > bay folded dipole antenna (not sure the mfg., but he thinks it's  
> > DB).
> > > Anyway, assuming that thing has useable SWR on my TX frequency (I've
> > > had that happen before, not holding my breath), does anyone have any
> > > ideas about the viability of running both repeaters on the same
> > > antenna but connecting the duplexer outputs together in to the  
> > common
> > > feedline? I've done no math, and not a lot of thinking, but is this
> > > one of those times when I might run odd multiples of 1/4 wave coax  
> > to
> > > a T at the hardline or something? Both repeaters have BpBr duplexers
> > > and both have isolators on their outputs.
> > >
> > > 73 DE N0MJS
> > >
> > > --
> > > Cort Buffington
> > > H: +1-785-838-3034
> > > M: +1-785-865-7206
> > >
> >
> >
> > 
> 
> --
> Cort Buffington
> H: +1-785-838-3034
> M: +1-785-865-7206
>

[Repeater-Builder] Re: Two Repeaters, One Antenna

[skipp025]

Good question... 

So what do you call a T-Connector with more than 3 ends on it? 

A T Connector with 4 coax ports/ends on it is called a 4-Way 

... or 4 Way Star. 

The "N" in N-Way is the number of available coax ports. 

Using the word "star" as a description can be tricky to those 
who think star points are restricted to certain numbers.

It's common in the transmitter antenna combiner world to see 
4-Way, 5-Way and sometimes 6-Way coax star units... good ones 
are expensive... easily costing hundreds of dollars. 

Telewave sells a crappy one in box form, which I avoid using. 
Sinclair makes one of the better N-Way coax stars and it's well 
worth the money. 

cheers, 
skipp 
skipp025 at yahoo.com 


> [EMAIL PROTECTED] wrote:
>
> Just what do you mean by an N-Way instead of the T connector, Never
heard
> of this.
> 
> Wesley AB8KD
>

[Repeater-Builder] Re: Two Repeaters, One Antenna

[Chris Huber]

How about taking the 16 bay, and splitting the harness in the middle and 
feed a second cable for the additional repeater.

Two antennas on one mast, less insertion loss, with combining the 2 
duplexers.

Or make the top antenna a Master receive and the bottom one transmit 
combined.


Chris N6ICW

[Repeater-Builder] Re: Two Repeaters, One Antenna

[Laryn Lohman]

--- In Repeater-Builder@yahoogroups.com, Chris Huber <[EMAIL PROTECTED]> wrote:
>
> How about taking the 16 bay, and splitting the harness in the middle
and 
> feed a second cable for the additional repeater.
> 
> Two antennas on one mast, less insertion loss, with combining the 2 
> duplexers.
> 
> Or make the top antenna a Master receive and the bottom one transmit 
> combined.
> 
> 
> Chris N6ICW
>

That'll work for the top half of a DB420; it's a complete antenna on
it's own.  What are you going to do with the coax port that fed the
top half?  You've got this open-ended coax stub that could do unknown
things to the characteristics of the bottom half.  

Laryn K8TVZ

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Jay Urish]

When I talk combiner, think duplexer on steriods..

Do a google search on hybrid combiner..

A combiner with give you several rx and tx ports..

ldgelectronics wrote:
> 
> 
> That's not much information. Please explain how that would be used.
> 
> Dwayne Kincaid
> WD8OYG
> 
> --- In Repeater-Builder@yahoogroups.com 
> , Jay Urish <[EMAIL PROTECTED]> 
> wrote:
>  >
>  > This is where you use a combiner...
>  >
>  >
>  >
> 
> 

-- 
Jay Urish W5GM  ex. KB5VPS

ARRL Life MemberDenton County ARRL VEC
N5ERS VP/Trustee

Monitoring 444.850 PL-88.5 146.92 PL-110.9

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Ken Arck]

At 12:18 PM 2/20/2008, you wrote:

>When I talk combiner, think duplexer on steriods..
>
>Do a google search on hybrid combiner..
>
>A combiner with give you several rx and tx ports..
<---Actually a combiner will give multiple TX ports. A multicoupler 
will give multiple RX Ports :-)

Ken
---
I am Shakespeare of Borg. Prepare to be or not to be

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[DCFluX]

Isolators work with transmitters only. That would do nothing for
getting signal from the antenna into the repeaters.

What you need is a diplexer. That is a low pass / high pass filter
network. These can be constructed with L/C high pass and low pass
filters, but that usually only has enough Q to work with a super wide
split, like VHF low pass and UHF high pass.

It looks more like you need a pair of interdigital band pass filters.

These can be tuned 5 MHz wide so the filter passes both TX and RX and
depending on the number of poles will be the isolation, I'd say 5
poles should be around -60dB,  20 MHz out.

They are kind of a pain to build as copper is expensive and aluminum
is really hard to weld, that aluminum solder crap never worked for me.

And then they are a real nutbuster to tune, don't even try it without
a spectrum analyzer with a tracking generator.

But before you spend any money, I would do a VSWR test with watt meter
and a hand held to see if the antenna is broad band enough to support
the 2 machines.

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[DCFluX]

BpBr duplexers only do wonders for the frequencies of intrest. That is the
TX and RX frequencies. The space in between the 2 is somewhat attenuated,
but the space outside the 2 frequencies is attenuated only -6 to -20dB
depending on the frequency spacing, number of cavities and who made the
duplexer.

This may seem alright, but -6dB down from 100 watts is still 25 watts.


On 2/20/08, Cort Buffington <[EMAIL PROTECTED]> wrote:
>
>  If the duplexers for each system are only 50 ohms at each receiver and
> transmitter, then I should see 4 frequencies where there is a 50 ohm load,
> and they are all different. Why would I need more than some sort of phasing
> harness to connect the two duplexers to the single transmission line,
> assuming the BpBr duplexers have enough isolation to keep the two repeaters
> from bothering each other?
>
> On Feb 20, 2008, at 2:22 PM, DCFluX wrote:
>
> Isolators work with transmitters only. That would do nothing for
> getting signal from the antenna into the repeaters.
>
> What you need is a diplexer. That is a low pass / high pass filter
> network. These can be constructed with L/C high pass and low pass
> filters, but that usually only has enough Q to work with a super wide
> split, like VHF low pass and UHF high pass.
>
> It looks more like you need a pair of interdigital band pass filters.
>
> These can be tuned 5 MHz wide so the filter passes both TX and RX and
> depending on the number of poles will be the isolation, I'd say 5
> poles should be around -60dB, 20 MHz out.
>
> They are kind of a pain to build as copper is expensive and aluminum
> is really hard to weld, that aluminum solder crap never worked for me.
>
> And then they are a real nutbuster to tune, don't even try it without
> a spectrum analyzer with a tracking generator.
>
> But before you spend any money, I would do a VSWR test with watt meter
> and a hand held to see if the antenna is broad band enough to support
> the 2 machines.
>
>
> --
> Cort Buffington
> H: +1-785-838-3034
> M: +1-785-865-7206
>
>
>
>
> 
>

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Cort Buffington]

If the duplexers for each system are only 50 ohms at each receiver and  
transmitter, then I should see 4 frequencies where there is a 50 ohm  
load, and they are all different. Why would I need more than some sort  
of phasing harness to connect the two duplexers to the single  
transmission line, assuming the BpBr duplexers have enough isolation  
to keep the two repeaters from bothering each other?


On Feb 20, 2008, at 2:22 PM, DCFluX wrote:


Isolators work with transmitters only. That would do nothing for
getting signal from the antenna into the repeaters.

What you need is a diplexer. That is a low pass / high pass filter
network. These can be constructed with L/C high pass and low pass
filters, but that usually only has enough Q to work with a super wide
split, like VHF low pass and UHF high pass.

It looks more like you need a pair of interdigital band pass filters.

These can be tuned 5 MHz wide so the filter passes both TX and RX and
depending on the number of poles will be the isolation, I'd say 5
poles should be around -60dB, 20 MHz out.

They are kind of a pain to build as copper is expensive and aluminum
is really hard to weld, that aluminum solder crap never worked for me.

And then they are a real nutbuster to tune, don't even try it without
a spectrum analyzer with a tracking generator.

But before you spend any money, I would do a VSWR test with watt meter
and a hand held to see if the antenna is broad band enough to support
the 2 machines.




--
Cort Buffington
H: +1-785-838-3034
M: +1-785-865-7206

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Jay Urish]

I stand corrected!


Ken Arck wrote:
> 
> 
> At 12:18 PM 2/20/2008, you wrote:
> 
>  >When I talk combiner, think duplexer on steriods..
>  >
>  >Do a google search on hybrid combiner..
>  >
>  >A combiner with give you several rx and tx ports..
> <---Actually a combiner will give multiple TX ports. A multicoupler
> will give multiple RX Ports :-)
> 
> Ken
> --
> I am Shakespeare of Borg. Prepare to be or not to be
> 
> 

-- 
Jay Urish W5GM  ex. KB5VPS

ARRL Life MemberDenton County ARRL VEC
N5ERS VP/Trustee

Monitoring 444.850 PL-88.5 146.92 PL-110.9

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Jay Urish]

Ken corrected me.. See his message--

Multicoupler..


ldgelectronics wrote:
> 
> 
> I know exactly what a hybrid combiner is (have several in use). I'm
> more curious to see how you propose to use that type of device to
> solve the problem that has been presented.
> 
> Dwayne Kincaid
> WD8OYG
> 
>  > When I talk combiner, think duplexer on steriods..
>  >
>  > Do a google search on hybrid combiner..
>  >
>  > A combiner with give you several rx and tx ports..
>  >
>  > ldgelectronics wrote:
>  > >
>  > >
>  > > That's not much information. Please explain how that would be
> used.
>  > >
>  > > Dwayne Kincaid
>  > > WD8OYG
>  > >
>  > > --- In Repeater-Builder@yahoogroups.com 
> 
>  > > , Jay Urish 
> wrote:
>  > > >
>  > > > This is where you use a combiner...
>  > > >
>  > > >
>  > > >
>  > >
>  > >
>  >
>  > --
>  > Jay Urish W5GM ex. KB5VPS
>  >
>  > ARRL Life Member Denton County ARRL VEC
>  > N5ERS VP/Trustee
>  >
>  > Monitoring 444.850 PL-88.5 146.92 PL-110.9
>  >
> 
> 

-- 
Jay Urish W5GM  ex. KB5VPS

ARRL Life MemberDenton County ARRL VEC
N5ERS VP/Trustee

Monitoring 444.850 PL-88.5 146.92 PL-110.9

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Mike Dietrich]

Cort,
contact me off list about this, i have som eideas you can use.
[EMAIL PROTECTED]
  - Original Message - 
  From: Cort Buffington 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Wednesday, February 20, 2008 2:29 PM
  Subject: Re: [Repeater-Builder] Re: Two Repeaters, One Antenna



  If the duplexers for each system are only 50 ohms at each receiver and 
transmitter, then I should see 4 frequencies where there is a 50 ohm load, and 
they are all different. Why would I need more than some sort of phasing harness 
to connect the two duplexers to the single transmission line, assuming the BpBr 
duplexers have enough isolation to keep the two repeaters from bothering each 
other?


  On Feb 20, 2008, at 2:22 PM, DCFluX wrote:


Isolators work with transmitters only. That would do nothing for
getting signal from the antenna into the repeaters.

What you need is a diplexer. That is a low pass / high pass filter
network. These can be constructed with L/C high pass and low pass
filters, but that usually only has enough Q to work with a super wide
split, like VHF low pass and UHF high pass.

It looks more like you need a pair of interdigital band pass filters.

These can be tuned 5 MHz wide so the filter passes both TX and RX and
depending on the number of poles will be the isolation, I'd say 5
poles should be around -60dB, 20 MHz out.

They are kind of a pain to build as copper is expensive and aluminum
is really hard to weld, that aluminum solder crap never worked for me.

And then they are a real nutbuster to tune, don't even try it without
a spectrum analyzer with a tracking generator.

But before you spend any money, I would do a VSWR test with watt meter
and a hand held to see if the antenna is broad band enough to support
the 2 machines.




  --
  Cort Buffington
  H: +1-785-838-3034
  M: +1-785-865-7206









   

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Wesley01]

Just what do you mean by an N-Way instead of the T connector, Never heard
of this.

Wesley AB8KD

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Cort Buffington]

T-1500 type is what's in the commercial repeater (micor). My repeater  
has a Wacom WP-678-R2 on it.


Odd multiples of 1/4 coax between duplexer tees and the antenna tee?

BTW: A big thanks to Skipp, Phil and the rest who've jumped in here  
today. I sometimes get some crazy notions (ham guy, not commercial 2- 
way shop here) and I really appreciate this group. I lurk a lot and  
learn a lot -- only hope I can give back more someday.


73 DE N0MJS

On Feb 20, 2008, at 5:08 PM, skipp025 wrote:



Seen and done this before...

Two Motorola T-1500 type duplexers, one setup on each repeater
along with the proper tx circulator for each. The antenna port of
both duplexers joined with another coax T... if you want to be
really on the money use a n-way and remove the two duplexer
output T's.

If the reflected power on the antennas is minimal the system
should play just fine. I've seen it done at more than one commercial
repeater site. The frequencies are far enough from each other
that everything should play just fine.

cheers,
s.

> Cort Buffington <[EMAIL PROTECTED]> wrote:
>
> Guys,
>
> I've found a site for my most recent Ham repeater project. Nice farm
> tower on a hill, clean of RF colo, etc. The farm repeater is a  
463.xxx
> + machine and I'm on 444.825. It is set up with nice hardline and  
a 16
> bay folded dipole antenna (not sure the mfg., but he thinks it's  
DB).

> Anyway, assuming that thing has useable SWR on my TX frequency (I've
> had that happen before, not holding my breath), does anyone have any
> ideas about the viability of running both repeaters on the same
> antenna but connecting the duplexer outputs together in to the  
common

> feedline? I've done no math, and not a lot of thinking, but is this
> one of those times when I might run odd multiples of 1/4 wave coax  
to

> a T at the hardline or something? Both repeaters have BpBr duplexers
> and both have isolators on their outputs.
>
> 73 DE N0MJS
>
> --
> Cort Buffington
> H: +1-785-838-3034
> M: +1-785-865-7206
>





--
Cort Buffington
H: +1-785-838-3034
M: +1-785-865-7206

RE: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Jeff DePolo]

 
> If the duplexers for each system are only 50 ohms at each 
> receiver and transmitter, then I should see 4 frequencies 
> where there is a 50 ohm load, and they are all different. Why 
> would I need more than some sort of phasing harness to 
> connect the two duplexers to the single transmission line, 
> assuming the BpBr duplexers have enough isolation to keep the 
> two repeaters from bothering each other?

Because your assumption that the duplexers will provide enough isolation
betwen Tx1 and Rx2 and Tx2 and Rx1 may be unrealistic.  On the receive side,
notches for a given duplexer are tuned to reject that duplexer's
transmitter, not the other transmitter.  Same for the transmit side - the
notches are tuned to notch that repeater's receive frequency, not the other
repeater's.  Am I saying it definately won't work?  No, it's far from being
a sure win.

Think about it this way.  Not only do you need adequate isolation between
your Tx and your Rx, but you also have to consider the isolation required
between your Tx and the other Rx, and between the other Tx and your Rx as
well.  Receiver-to-receiver isolation is likely not an issue unless you have
LO leakage issues.  Of course, do the math to make sure you don't have any
intermod hits either...

For the heck of it I just swept a 4-cavity duplexer (Decibel DB4076W) on the
VNA to see what the response looked like.  With the duplexer tuned for
444/449 MHz, I looked at the transmission response from the the transmitter
port to the antenna port.  The duplexer provides about 46 dB of attenuation
at the 468 MHz receive frequency, i.e. the isolation from your Tx to their
Rx would only be 46 dB + whatever insertion loss is in their duplexer
(probably about 1 dB).  And that appears to be the best case scenario.  If
you look at the other side of the notch (lower in frequency), the response
is much less, so the same duplexer used for the 463/468 box would likely
provide little (on the order of 20 dB) of attenuation of the other
repeater's transmitter noise at your receive frequency.  I can guarantee you
that having only 20 dB of noise supression will make you very sad.

The better the front end of the receiver, the less Tx carrier supression you
will need.  The cleaner the transmitter, the less noise supression you will
need.  Those rules hold true whether you're talking about one repeater, two
repeaters, or ten repeaters.  Without knowing exactly what you have, and
they have, as far as equipment, it's hard to guess how much isolation you're
really going to need from any port to any other port.

If you had two "true" bandpass duplexers at your disposal, each of which had
adequate isolation at the standard 5 MHz split to prevent desense when used
in a single-repeater application, you would likely make out OK by teeing
them together with appropriate-length cables since your Rx is close to 14
MHz away from their Tx, i.e. significantly further than the 5 MHz away your
own Tx is, and therefore, that much more attenuation could be expected due
to the bandpass characteristics of the filters.

A simple solution, if you don't want to replace duplexers, would be to use
two window filters, one tuned to pass the ham Tx and Rx, and the other tuned
to pass the commercial Tx and Rx, and tee them together with the
appropriate-length cables (which will vary based on the design of the
filters, and is something best left to be done on a network analyzer).
This, of course, assumes that the skirts on the window filters are steep
enough to make up the additional isolation required to avoid desense between
systems.

This could also be done with a 4-port combiner/multicoupler, but would
likely require 8 to 12 cavities total to accomplish (a combination of pass
and pass/reject most likely).  I've built transmit/receive combiners for a
number of ham projects, including one where I have a 442/447 ham repeater
combined with a 450/455 MHz repeater.  That one took 10 cavities and two
single-stage isolators to achieve the required isolation, as well as provide
adequate Rx filtering to avoid desense from other co-located stations.

Why not just put up a separate antenna?

--- Jeff WN3A

Re: [Repeater-Builder] Re: Two Repeaters, One Antenna

[Cort Buffington]

Folks,

Thanks for the input, but changing the configuration of the commercial  
repeater is not an option. I'll probably do a little tinkering, then  
end up putting up a separate antenna for my repeater below the other  
one. My reason for doing this is that it would have avoided me buying  
more hardline and using something like a Hustler G6-440 instead of  
being able to use that huge 16 bay antenna. Again, thanks for the input.

73 DE N0MJS

On Feb 21, 2008, at 7:49 AM, Laryn Lohman wrote:

> --- In Repeater-Builder@yahoogroups.com, Chris Huber <[EMAIL PROTECTED]>  
> wrote:
> >
> > How about taking the 16 bay, and splitting the harness in the middle
> and
> > feed a second cable for the additional repeater.
> >
> > Two antennas on one mast, less insertion loss, with combining the 2
> > duplexers.
> >
> > Or make the top antenna a Master receive and the bottom one transmit
> > combined.
> >
> >
> > Chris N6ICW
> >
>
> That'll work for the top half of a DB420; it's a complete antenna on
> it's own. What are you going to do with the coax port that fed the
> top half? You've got this open-ended coax stub that could do unknown
> things to the characteristics of the bottom half.
>
> Laryn K8TVZ
>
>
> 





 
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