Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?

2016-03-24 Thread Jim Brown

On Wed,3/23/2016 11:38 PM, Mark van Wijk, PA5MW wrote:
The problem is that while listening to your receiving antennas, there 
is also some signal from the transmit antenna getting through thanks 
to the internal cross-talk of your rig's TX/RX relay. 


There are many heads to this snake, but also many fixes. This post is 
about crosstalk, NOT interaction. First, there is coupling between the 
antennas themselves. Cross-band interference between transmit antennas 
can be greatly reduced by the use of bandpass filters, but these filters 
don't help with RX antennas not within the filter loop.


Second, there is coupling due to leakage capacitance between relays, 
poor layout of relay boxes, and currents within our stations. My station 
uses a 6x2 relay box to distribute monoband antennas between rigs for 
SO2R, but some have a lot more crosstalk than others. Last spring, I 
replaced an Array Solutions Six-Pak with a 4O3A box. I measured both 
boxes for isolation using the DG8SAQ VNWA -- the 4O3A unit had more than 
20 dB better isolation than the SixPak.


But even with that improvement in hardware, I still found isolation 
insufficient, so I bought a spool of BuryFlex and a box of Amphenol 
83-1SP (solder-type coax connectors) and replaced every piece of coax in 
my station and made sure that all were wrench-tight. (I didn't count, 
but I'd guess about 25 cables). That provided another 10 dB or so (not 
measured, but looking at P3 traces while operating).


Another issue I still need to address is bandpass filters on RX 
antennas. I often use my Beverages up to 30M. My K3 can handle the 
signal strength without damage, but while contesting, I hear very strong 
harmonics there.


In one of the early chapters of his classic book, "Managing Interstation 
Interference," W2VJN advises us to begin by measuring the coupling 
between our antennas so that we understand the levels of crosstalk that 
can be present. It's easy to do that with a vector network analyzer like 
the DG8SAQ VNWA. [Note that antenna analyzers are NOT network analyzers 
-- they are single-port devices. The difference is that a VNA is a 
2-port device, so it can measure BOTH impedance and the gain (or loss) 
between input and output ports.] We can, of course, make these 
measurements with gear as simple as an amplitude-calibrated RF generator 
and a calibrated voltmeter (anything from a scope to a spectrum analyzer).


The VNWA 3e is a real bargain. It's full spec to 500 MHz, reduced spec 
to 1.3 GHz, and self-powers from the USB connection to your computer. I 
paid about $750 shipped to my home in W6 about 3 years ago for a unit 
with calibration kit.


http://sdr-kits.net/VNWA3_Description.html

73, Jim K9YC
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Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do?

2016-03-24 Thread Mark van Wijk, PA5MW

Good point.

On 160 there was also a relatively nearby 829KHz AM BC station.
The RDX PI4YLC Field-Day-style  station used an OM-Power 6 BPF in its TX 
path.

But no additional BPF or AM BCB HP filter in the RX path.
A mistake I should have recognized.

Thanks for the test procedure.
Will use that additionally  for sure at home and at any FD QTH in the 
future.


73 Mark, PA5MW


-Original Message- 
From: JC

Sent: Thursday, March 24, 2016 1:14 PM
To: 'Mark van Wijk, PA5MW' ; 'william radice' ; topband@contesting.com
Subject: Re: Topband: Post contest season: TX antenna vs RXantenna 
cros-stalk. What do you do?



I was wondering what people do besides the obvious 'kill the TX antenna

input during RX mode' ?<<

There are several reasons why it is necessary to detune the TX antenna
during RX, however disconnecting the center of the TX coax during RX on 160m
is a MUST.

If you don't understand the problem you never implement the solution. Some
broadcast signal can reach -10 dbm or even 0 dbm. Most radios have very poor
isolation and pin 1 problem on both the RX input and TX input.

In order to open the center pin at the antenna feed point you need  a fast
vacuum relay to avoid hot switch. For an inverted L it will improve all RX
antennas removing re-radiation noise from the TX antenna.

Open the circuit between the transverter and the amplifier is a good idea.
You need a fast relay but it can be small.

Filters must be strong enough to hold at least 200w  with low insertion
loss.

The test to know if you have this problem is simple, disconnect the RX
antenna and use a 50ohms, shielded load to terminate the RX input. Tune on
the AM band and if you hear strong BC signals coming from you TX antenna
during RX with the RX port terminated with 50 ohms you have some homework to
do.

No carriers at all indicate that you have shield, grounding and choking in
good shape, if you hear strong AM signals means that you have isolation and
common node noise problems. If the BC signal can come in all QRN and other
noise sources also can come in and raise the noise floor of the receiver.

My station is quiet, I cannot detect any trace or light carrier doing the
test above.

Regards
JC
N4IS


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Re: Topband: Post contest season: TX antenna vs RX antennacros-stalk. What do you do?

2016-03-24 Thread Mark van Wijk, PA5MW

Hi Kees,

That is what I successfully do at home, because my 160m vertical re-radiates 
to my RX antennes.


But at the recent RDXC PI4YLC FD contest station both the 40 and 80m 
full-size deltaloops were not detuned or switched to GND or anything.
The YL ops wanted to be able to listen to them as well as the separate RX 
antennes anyway.


73 Mark, PA5MW


-Original Message- 
From: Kees Nijdam

Sent: Thursday, March 24, 2016 11:05 AM
To: Mark van Wijk, PA5MW
Subject: Re: Topband: Post contest season: TX antenna vs RX 
antennacros-stalk. What do you do?


Hi Mark,

When receiving on my RX antennas, my transmit verticals are detuned by
decoupling them from the feedline.
A floating 1/4 wave verical is completely dead and not reradiating signals.

Kees, PE5T

--
From: "Mark van Wijk, PA5MW" 
Sent: Thursday, March 24, 2016 7:38 AM
To: "william radice" ; 
Subject: Re: Topband: Post contest season: TX antenna vs RX
antennacros-stalk. What do you do?


Hi Bill,

I think this is not what I meant here; I also do use BPF's and the Front 
End Savers.


The problem is that while listening to your receiving antennas, there is 
also some signal from the transmit antenna getting through thanks to the 
internal cross-talk of your rig's TX/RX relay.


I was wondering what people do besides the obvious 'kill the TX antenna 
input during RX mode' ?


73 Mark, PA5MW



-Original Message- 
From: william radice

Sent: Tuesday, March 22, 2016 2:05 PM
To: topband@contesting.com
Subject: Re: Topband: Post contest season: TX antenna vs RX antenna 
cros-stalk. What do you do?


 Serious multi-op contest stations face this issue all the time.
Most use individual band filters and they almost completely eliminate
the issue.
At our station we used the Dunestar filters for operating positions on
different bands. As for 160 I personally use the KD9SV "front end saver"
and it does the job completely.
BILL K4OWR

On 3/22/2016 5:44 AM, Mark van Wijk wrote:
Now that we are  'sort of in post contest season mode' and sharing some 
good

ideas, there is another question:

During recent Field-day setups I noticed severe cross-talk issues between 
TX

antennas and the separate RX antenna circuits.
For sure any TX/R relay circuitry offers roughly 50-65 dB dampening. So, 
during
a contest with >S9+30 signals received on the large TX antennas 
(Deltaloop for
40m and 80m) these would still show up S1 - S4 on the FD station's K3 RX 
input.
At home I normally de-tune my backyard TX antenna(switch to GND during 
RX) to

avoid noise pickup at the RX antennas, so I never noticed this.


Question 1: how do you manage the TX-RX cross-talk at your setup?

- switch TX antenna to GND during RX
- switch-in en external attenuator, so the cross-talk is below noise 
level, but

you are still able to use the TX antenna during RX
- any other solution?


Question 2: is there any other basic circuitry or setup in a basic 
contest

station which offer possible similar negative side effects?



73, Mark PA5MW
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Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do?

2016-03-24 Thread Mark van Wijk, PA5MW

Hi Terry,

I have no access to the K3's as they belong to  someone else.
But I learned there  is no such thing as  total  isolation.
Not even with the Frond end savers, unless they incorporate several relays 
in series.


But I did check my TT ORION using the Elecraft XG3 generator; isolation is 
abt 65dB
You do the math when you have 9+40 signals on a large antenna like a 
fullsize TX deltaloop on 40 & 80m



73 Mark, PA5MW




-Original Message- 
From: Terry Posey

Sent: Thursday, March 24, 2016 12:04 PM
To: 'Mark van Wijk, PA5MW' ; 'william radice' ; topband@contesting.com ; 
Eric Swartz -WA6HHQ, Elecraft
Subject: Re: Topband: Post contest season: TX antenna vs RXantenna 
cros-stalk. What do you do?


Hi Mark -

I have not experienced K3 TX/RX antenna isolation problems with my station
configuration.  I expect that if there is an isolation problem with your
rig's TX and external RX antenna routing/switching, that problem would be
nearly impossible to quantify using your station's TX and RX antennas.  The
rig's TX/RX isolation would need to be measured on the bench, using good
laboratory grade equipment.

Perhaps, Elecraft can provide a list of expected isolation values that were
measured for each of the TX and external RX antenna routing/switching
configurations possible with the K3 and K3S.  Those measurements would
surely have been done during the rigs' design performance verification
tests.

GL

73,
Terry K4RX

++
Hi Bill,

I think this is not what I meant here; I also do use BPF's and the Front End
Savers.

The problem is that while listening to your receiving antennas, there is
also some signal from the transmit antenna getting through thanks to the
internal cross-talk of your rig's TX/RX relay.

I was wondering what people do besides the obvious 'kill the TX antenna
input during RX mode' ?

73 Mark, PA5MW

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Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?

2016-03-24 Thread JC
>>I was wondering what people do besides the obvious 'kill the TX antenna
input during RX mode' ?<<

There are several reasons why it is necessary to detune the TX antenna
during RX, however disconnecting the center of the TX coax during RX on 160m
is a MUST. 

If you don't understand the problem you never implement the solution. Some
broadcast signal can reach -10 dbm or even 0 dbm. Most radios have very poor
isolation and pin 1 problem on both the RX input and TX input.

In order to open the center pin at the antenna feed point you need  a fast
vacuum relay to avoid hot switch. For an inverted L it will improve all RX
antennas removing re-radiation noise from the TX antenna.

Open the circuit between the transverter and the amplifier is a good idea.
You need a fast relay but it can be small.

Filters must be strong enough to hold at least 200w  with low insertion
loss.

The test to know if you have this problem is simple, disconnect the RX
antenna and use a 50ohms, shielded load to terminate the RX input. Tune on
the AM band and if you hear strong BC signals coming from you TX antenna
during RX with the RX port terminated with 50 ohms you have some homework to
do.

No carriers at all indicate that you have shield, grounding and choking in
good shape, if you hear strong AM signals means that you have isolation and
common node noise problems. If the BC signal can come in all QRN and other
noise sources also can come in and raise the noise floor of the receiver.

My station is quiet, I cannot detect any trace or light carrier doing the
test above. 

Regards
JC 
N4IS


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Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?

2016-03-24 Thread Filipe Lopes
I am using 2xTS590 and never had any issues either.

73s Filipe
CT1ILT CR6K

Sent from my Huawei Mate 8
Em 24/03/2016 12:05 p.m., "Terry Posey"  escreveu:

> Hi Mark -
>
> I have not experienced K3 TX/RX antenna isolation problems with my station
> configuration.  I expect that if there is an isolation problem with your
> rig's TX and external RX antenna routing/switching, that problem would be
> nearly impossible to quantify using your station's TX and RX antennas.  The
> rig's TX/RX isolation would need to be measured on the bench, using good
> laboratory grade equipment.
>
> Perhaps, Elecraft can provide a list of expected isolation values that were
> measured for each of the TX and external RX antenna routing/switching
> configurations possible with the K3 and K3S.  Those measurements would
> surely have been done during the rigs' design performance verification
> tests.
>
> GL
>
> 73,
> Terry K4RX
>
> ++
> Hi Bill,
>
> I think this is not what I meant here; I also do use BPF's and the Front
> End
> Savers.
>
> The problem is that while listening to your receiving antennas, there is
> also some signal from the transmit antenna getting through thanks to the
> internal cross-talk of your rig's TX/RX relay.
>
> I was wondering what people do besides the obvious 'kill the TX antenna
> input during RX mode' ?
>
> 73 Mark, PA5MW
>
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
>
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Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?

2016-03-24 Thread Terry Posey
Hi Mark -

I have not experienced K3 TX/RX antenna isolation problems with my station
configuration.  I expect that if there is an isolation problem with your
rig's TX and external RX antenna routing/switching, that problem would be
nearly impossible to quantify using your station's TX and RX antennas.  The
rig's TX/RX isolation would need to be measured on the bench, using good
laboratory grade equipment.

Perhaps, Elecraft can provide a list of expected isolation values that were
measured for each of the TX and external RX antenna routing/switching
configurations possible with the K3 and K3S.  Those measurements would
surely have been done during the rigs' design performance verification
tests.  

GL

73,
Terry K4RX

++
Hi Bill,

I think this is not what I meant here; I also do use BPF's and the Front End
Savers.

The problem is that while listening to your receiving antennas, there is
also some signal from the transmit antenna getting through thanks to the
internal cross-talk of your rig's TX/RX relay.

I was wondering what people do besides the obvious 'kill the TX antenna
input during RX mode' ?

73 Mark, PA5MW 

_
Topband Reflector Archives - http://www.contesting.com/_topband


Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?

2016-03-24 Thread Mark van Wijk, PA5MW

Hi Bill,

I think this is not what I meant here; I also do use BPF's and the Front End 
Savers.


The problem is that while listening to your receiving antennas, there is 
also some signal from the transmit antenna getting through thanks to the 
internal cross-talk of your rig's TX/RX relay.


I was wondering what people do besides the obvious 'kill the TX antenna 
input during RX mode' ?


73 Mark, PA5MW



-Original Message- 
From: william radice

Sent: Tuesday, March 22, 2016 2:05 PM
To: topband@contesting.com
Subject: Re: Topband: Post contest season: TX antenna vs RX antenna 
cros-stalk. What do you do?


 Serious multi-op contest stations face this issue all the time.
Most use individual band filters and they almost completely eliminate
the issue.
At our station we used the Dunestar filters for operating positions on
different bands. As for 160 I personally use the KD9SV "front end saver"
and it does the job completely.
BILL K4OWR

On 3/22/2016 5:44 AM, Mark van Wijk wrote:
Now that we are  'sort of in post contest season mode' and sharing some 
good

ideas, there is another question:

During recent Field-day setups I noticed severe cross-talk issues between 
TX

antennas and the separate RX antenna circuits.
For sure any TX/R relay circuitry offers roughly 50-65 dB dampening. So, 
during
a contest with >S9+30 signals received on the large TX antennas (Deltaloop 
for
40m and 80m) these would still show up S1 - S4 on the FD station's K3 RX 
input.
At home I normally de-tune my backyard TX antenna(switch to GND during RX) 
to

avoid noise pickup at the RX antennas, so I never noticed this.


Question 1: how do you manage the TX-RX cross-talk at your setup?

- switch TX antenna to GND during RX
- switch-in en external attenuator, so the cross-talk is below noise 
level, but

you are still able to use the TX antenna during RX
- any other solution?


Question 2: is there any other basic circuitry or setup in a basic contest
station which offer possible similar negative side effects?



73, Mark PA5MW
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