advice on buying second-hand network analyzer

Thread Starter

bug13

Joined Feb 13, 2012
2,002
Hi guys

I want to get more hand on, and learn about more about antenna matching and tuning, so I need a VNA. New ones are too expensive for me, so I want to get my hand on a second-hand one.

I see this on ebay:
Keysight Agilent HP 8711C 300 kHz to 1.3 GHz
http://www.ebay.com/itm/Keysight-Ag...530939?hash=item28223416fb:g:6toAAOSwYIxX~jTQ

What do you guys think? I would love you hear your advice/suggestion before parting my money.

Cheers.

James
 
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Papabravo

Joined Feb 24, 2006
21,094
Hi guys

I want to get more hand on, and learn about more about antenna matching and tuning, so I need a VNA. New ones are too expensive for me, so I want to get my hand on a second one.

I see this on ebay:
Keysight Agilent HP 8711C 300 kHz to 1.3 GHz
http://www.ebay.com/itm/Keysight-Ag...530939?hash=item28223416fb:g:6toAAOSwYIxX~jTQ

What do you guys think? I would love you hear your advice/suggestion before parting my money.

Cheers.

James
Good Luck finding 3.5" floppy discs to use with it. Doesn't look like it comes with any probes, adapters, or test jigs. That price seems way too low for what you think it might be. You probably cannot get it repaired or calibrated if it is more than 20 years old. Try to run down a PDF of the manual so you can see what is required to make it work.
 

GopherT

Joined Nov 23, 2012
8,009
Hi guys

I want to get more hand on, and learn about more about antenna matching and tuning, so I need a VNA. New ones are too expensive for me, so I want to get my hand on a second one.

I see this on ebay:
Keysight Agilent HP 8711C 300 kHz to 1.3 GHz
http://www.ebay.com/itm/Keysight-Ag...530939?hash=item28223416fb:g:6toAAOSwYIxX~jTQ

What do you guys think? I would love you hear your advice/suggestion before parting my money.

Cheers.

James

James, just an English usage tip. Getting s "second one" means you already have a first one. The phrase you are looking for is "a second-hand one". Or a "used one".

Reading the title alone, I thought you already had a first one and needed a second one with different features. When I read the post, the context inducated you were looking for s used network analyzer.

Cheers.
 

Thread Starter

bug13

Joined Feb 13, 2012
2,002
James, just an English usage tip. Getting s "second one" means you already have a first one. The phrase you are looking for is "a second-hand one". Or a "used one".

Reading the title alone, I thought you already had a first one and needed a second one with different features. When I read the post, the context inducated you were looking for s used network analyzer.

Cheers.
I was actually thinking second hand one, but somehow I typed second one, Doh!!

If someone can edit the title for me please, I don't seem to find a edit title button.
 

Thread Starter

bug13

Joined Feb 13, 2012
2,002
Good Luck finding 3.5" floppy discs to use with it. Doesn't look like it comes with any probes, adapters, or test jigs. That price seems way too low for what you think it might be. You probably cannot get it repaired or calibrated if it is more than 20 years old. Try to run down a PDF of the manual so you can see what is required to make it work.
I am now looking at this one(miniVNA):
http://miniradiosolutions.com/54-2/

It doesn't seem to come with cable, what sort of cable do I need, just simple 50Ohm coax? or some sort of special cable? I assume the cable needs to be able to handle the full range right? (up to 3GHz)
 

Papabravo

Joined Feb 24, 2006
21,094
I am now looking at this one(miniVNA):
http://miniradiosolutions.com/54-2/

It doesn't seem to come with cable, what sort of cable do I need, just simple 50Ohm coax? or some sort of special cable? I assume the cable needs to be able to handle the full range right? (up to 3GHz)
Most types of 50Ω coax are not compatible with SMA connectors. You can use "tweenies" to convert SMA to BNC or other types of connectors. I have an earlier version of this device and it works well for Amateur Radio applications including antenna characterization and experimentation.
 
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Thread Starter

bug13

Joined Feb 13, 2012
2,002
Most types of 50Ω coax are not compatible with SMA connectors. You can use "tweenies" to convert SMA to BNC or other types of connectors. I have an earlier version of this device and it works well for Amateur Radio applications including antenna characterization and experimentation.
So I can use a 50ohm cable with the right connector? For playing around antenna turning and matching?
 

Thread Starter

bug13

Joined Feb 13, 2012
2,002
Yes, or you can use your normal cable with an adapter that has a normal connector on one side and an SMA connector on the other. We call these adapters "tweenies" because they go in between two connector types.

https://www.amazon.com/Maxmoral-PL-...r=8-1-spons&keywords=pl+259+to+sma+male&psc=1
Just to make sure I understand it correctly, so a 50ohm cable can test an antenna for 304Mhz, 433Mhz, 915Mhz, 2.4Ghz etc..?? I thought impedance is depending on the frequency??
 
i think the title editing menu is around for normal people. It's just not easy to get to.

The term "tracking generator" comes up a lot. It's preferred if the instrument has one. It's like a marker.

The inputs look like N connectors and that's not unusual.

There are Floppy emulators. That's almost a given you'll have to replace that. Full size floppy drives even have network file systems. Slim drives usually do not.
 

Papabravo

Joined Feb 24, 2006
21,094
Just to make sure I understand it correctly here. A 50ohm cable can be use to test antenna for 304Mhz, 433Mhz, 800Mhz, 915Mhz, 2.4Ghz, all these bands?

PS: I got this when I google "tweenies":
https://www.google.co.nz/search?q=t...8crTAhUBSJQKHRCeDT0Q_AUICigB&biw=1920&bih=974
The characteristic impedance depends on the geometry of the cable. The loss per foot goes up with frequency. Look at the datasheet for RG-8/U and then look at LMR-400. Notice the difference in loss between the two?

You might find the following article helpful

https://en.wikipedia.org/wiki/Coaxial_cable
 
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Thread Starter

bug13

Joined Feb 13, 2012
2,002
The characteristic impedance depends on the geometry of the cable. The loss per foot goes up with frequency. Look at the datasheet for RG-8/U and then look at LMR-400. Notice the difference in loss between the two?

You might find the following article helpful

https://en.wikipedia.org/wiki/Coaxial_cable
The wiki is very helpful.

I know the lower the lose the better, but for my application (antenna matching and turning), I can still use a RG-8/U cable right? I mean I can still see the resonance frequency of an antenna (so I can turn it), and I can still see the impedance of antenna right (so I can match the impedance)? But the lose will be bigger when using a RG-8/U cable instead of a LMR-400 cable?

Or the calibration process the a VNA can somehow compensate these (to a degree maybe?), because usually people will keep the cable as short as possible?
 
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