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VSWR Terminator

R

rjkfsm

Jan 1, 1970
0
Hi,

I need to test some antenna's. The customer wants them tested by
sweeping with the operating frequencies (1MHz to 3GHz) by using a
tracking generator, bi-diectional coupler, a spectrum analyzer and VSWR
terminators. The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator. This is the procedure the
customer wants and the customer is a 400lb gorilla. The customer gets
what the customer wants.

Does anyone know where I can get relatively high precision VSWR
terminators with 'N' or 'BNC' connectors? I need: 1.8:1 (90 Ohms), 1.9:1
(95 Ohms), 2.0:1 (100 Ohms), 3.0:1 (150 Ohms) and 3.5:1 (175 Ohms). 'N'
connector is prefered, but BNC is acceptable.

RK
 
R

Robert Baer

Jan 1, 1970
0
rjkfsm said:
Hi,

I need to test some antenna's. The customer wants them tested by
sweeping with the operating frequencies (1MHz to 3GHz) by using a
tracking generator, bi-diectional coupler, a spectrum analyzer and VSWR
terminators. The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator. This is the procedure the
customer wants and the customer is a 400lb gorilla. The customer gets
what the customer wants.

Does anyone know where I can get relatively high precision VSWR
terminators with 'N' or 'BNC' connectors? I need: 1.8:1 (90 Ohms), 1.9:1
(95 Ohms), 2.0:1 (100 Ohms), 3.0:1 (150 Ohms) and 3.5:1 (175 Ohms). 'N'
connector is prefered, but BNC is acceptable.

RK
BNC connectors are rather indecent going up to three giggles; use H,
HN, or GR.
 
B

bart

Jan 1, 1970
0
Hi,

I need to test some antenna's. The customer wants them tested by
sweeping with the operating frequencies (1MHz to 3GHz) by using a
tracking generator, bi-diectional coupler, a spectrum analyzer and VSWR
terminators. The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator. This is the procedure the
customer wants and the customer is a 400lb gorilla. The customer gets
what the customer wants.

Does anyone know where I can get relatively high precision VSWR
terminators with 'N' or 'BNC' connectors? I need: 1.8:1 (90 Ohms), 1.9:1
(95 Ohms), 2.0:1 (100 Ohms), 3.0:1 (150 Ohms) and 3.5:1 (175 Ohms). 'N'
connector is prefered, but BNC is acceptable.

RK
I'd like to see the 1 MHz antenna next to the 3 Gig unit!
That sort of testing sounds a bit weird.
A quick & dirty way is just using a Bird antenna analyser, a bit
pricey but they get results fast. ( nothing up to 3 gig though)
http://www.tessco.com/products/displaySkus.do?groupId=490&subgroupId=10
 
R

Russ

Jan 1, 1970
0
rjkfsm said:
Hi,

I need to test some antenna's. The customer wants them tested by
sweeping with the operating frequencies (1MHz to 3GHz) by using a
tracking generator, bi-diectional coupler, a spectrum analyzer and VSWR
terminators. The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator. This is the procedure the
customer wants and the customer is a 400lb gorilla. The customer gets
what the customer wants.

Does anyone know where I can get relatively high precision VSWR
terminators with 'N' or 'BNC' connectors? I need: 1.8:1 (90 Ohms), 1.9:1
(95 Ohms), 2.0:1 (100 Ohms), 3.0:1 (150 Ohms) and 3.5:1 (175 Ohms). 'N'
connector is prefered, but BNC is acceptable.

RK


OK, these are for a ship, so yes all the antenna's will be closely placed on
a mast, however great thought by minds sharper than mine have devoted
themselves to a layout that utilizes harmonics, dead zones, shadowing and
ground planes to prevent interference.

The antenna's are fed by heliac and most of the connectors are 'N' which
would eliminate the need for adaptors. There are some H and HG connectors
as well, but using adaptors for testing these is acceptable to the
customer. Most of the adaptors we have are to or from 'N' style, so that is
the preferred style of connector in our lab.

Again, this customer is a 400lb gorilla. They have decided already how they
want the antenna's tested. There is no altering what they want. I cannot
use an SWR meter. Period. I wish I could. I already have several and it
would make my life so much easier.

Don't get me wrong: Thank you for your time in responding, however it does
not meet what I need.

RK
 
T

Theo v. Werkhoven

Jan 1, 1970
0
The carbonbased lifeform rjkfsm inspired sci.electronics.equipment with:
Hi,

I need to test some antenna's. The customer wants them tested by
sweeping with the operating frequencies (1MHz to 3GHz) by using a
tracking generator, bi-diectional coupler, a spectrum analyzer and VSWR
terminators. The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator. This is the procedure the
customer wants and the customer is a 400lb gorilla. The customer gets
what the customer wants.

With the setup you describe the return loss is directly read from the SA
when you attach the antennae, no need for an extra calibration.
All you need to care about is the directivity of the coupler, which
needs to better than the return loss you expect.
Does anyone know where I can get relatively high precision VSWR
terminators with 'N' or 'BNC' connectors? I need: 1.8:1 (90 Ohms), 1.9:1

Nop, sorry.

Theo
 
F

Fred Abse

Jan 1, 1970
0
The procedure is to hook up all equipment through the
production cable with the test terminator at the end and use that to set
the spec an to mid scale and mark. Then attach the actual antenna and
ensure that VSWR is less than the terminator

Am I missing something here? Is your 400lb gorilla expecting his antennas
to exhibit a lower VSWR than a precision termination?

I'd be more worried about finding directional coupler(s) with sufficient
isolation over that frequency range than finding precision terminations,
which are fairly plentiful.

Dunno how long your cables are, but their attenuation will mask out small
mismatches, anyway, especially at the top end.
 
G

Glenn

Jan 1, 1970
0
rjkfsm

How about using some known attenuators with either shorts or opens on
the far end to generate a precision reference R and therby a known VSWR,
assuming Heliax, connectors and all are OK.
Errors in this value along with directivity of the dual directional
coupler reduce margin but it's unlikely that they are bad compared to
antennas in the environment you describe.

If you don't want to do the math, you should be able to measure the
input resistance of a decent attenuator terminated in a short or open
(keep it the same for all measurements) and safely assume that the R is
constant with frequency and the the parallel Z is very high.

If you don't mind doing the math, you can validate your method for the
gorilla too.

Glenn
 

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