Have a real newbie ?

[Dutchman11]

Can I use the same swr meter that I use for my 11 meter cb to check the swr on my 2 meter radio. Have not got the connections yet to try but the thought just crossed my mind if there is a difference.

 

[w9cll]

In a short answer... no. You will need a VHF meter

 

[C2]

Many will say no because the frequency is far outside its design range, and that would be true that the number you get will not be anywhere near accurate.

But

SWR is really a relative measurement anyway and you can use your meter to find and set the lowest SWR. You just won't know what it is, exactly....

for example, your meter might show an SWR of 9:1 but the actual SWR might be 2:1. All that matters is that you find and adjust for the lowest SWR.

It's kind of risky in that your SWR might actually be high and you would not know it. You can mitigate that though once you've checked your system and compared your HF meter with a known good meter.

 

[Dutchman11]

This is what I have. A Boafeng UV 5r v2 and purchased a 2 meter mobile magnetic mount antenna that is not adjustable and from past cb experience you always check the swr. I just got my Tech ticket and it is a whole new ball game. So I guess I will be investing in an analyzer any suggestions? Next radio I am looking at is a Yaesu 857d.

 

[C2]

Well, if it's not adjustable, the last thing you want to do is measure it!

I bought an SX-144/440 something like that cross-needle meter, just to have a wee bit of piece of mind.

No reason to worry much about it, just buy more radio gear. Talk more, measure less.

 

[w9cll]

Many will say no because the frequency is far outside its design range, and that would be true that the number you get will not be anywhere near accurate.

But

SWR is really a relative measurement anyway and you can use your meter to find and set the lowest SWR. You just won't know what it is, exactly....

for example, your meter might show an SWR of 9:1 but the actual SWR might be 2:1. All that matters is that you find and adjust for the lowest SWR.

It's kind of risky in that your SWR might actually be high and you would not know it. You can mitigate that though once you've checked your system and compared your HF meter with a known good meter.

Ahh still no you need a vhf one.

 

[Captain Kilowatt]

The problem with using a CB type meter on VHF is that the sensing circuit is nowhere near anything representing 50 ohms on VHF. If, and I do say IF, it simply measures a minimum SWR how do you know it really is the lowest you can get? The meter may have a weird frequency response and be anything but flat. You don't need anything expensive for 2m but you definitely should have a meter rated for the frequency range you are using. Many,many years ago I bought a Diamond SX-1000 meter that is good for 200 watts and reads SWR in four ranges covering HF, VHF including 2m, UHF including 70 cm, and another UHF band covering 800 MHz cellular/PCS and the 1.2 GHz band. Best thing I ever did as far as meters go.

 

[binrat]

I have never tried this but I have heard from someone that if you use a cheapo hf meter just calibrate like normal and then switch the cables around to show reflected back. Again I have never tried it.

Sent from my GT-S5690M using Tapatalk 2

 

[W5LZ]

And by doing that switching around you have a forward and reverse reading watt meter, not an SWR meter. You would have to do the converting of those readings to get SWR. Or, like those 'cross-needle' meters, you could calibrate an SWR scale. Lot of trouble though. That SWR scale is not linear...
- 'Doc

 

[C2]

The problem with using a CB type meter on VHF is that the sensing circuit is nowhere near anything representing 50 ohms on VHF. If, and I do say IF, it simply measures a minimum SWR how do you know it really is the lowest you can get? The meter may have a weird frequency response and be anything but flat. You don't need anything expensive for 2m but you definitely should have a meter rated for the frequency range you are using. Many,many years ago I bought a Diamond SX-1000 meter that is good for 200 watts and reads SWR in four ranges covering HF, VHF including 2m, UHF including 70 cm, and another UHF band covering 800 MHz cellular/PCS and the 1.2 GHz band. Best thing I ever did as far as meters go.

My suspicion is that the basic schematic for these low-end type meters are all basically the same, with a matched strip-line capacitively coupled to a very simple detector circuit. The problem lies there within the detector, the five cent diode that is certainly to have considerable rolloff with increased frequency, not to mention the coupling arrangement.

However, if that detector can put out enough current to drive the meter, which it usually can, then you will get a relative indication.

It works if you understand what's happening.

http://www.qsl.net/n9zia/wireless/pics/turd_wattmeter.png

You will know it's the lowest SWR because the detector will not detect as much reflected RF. The detector circuit certainly is not going to produce a current on it's own, so there is either RF or not, and the degree is relative.

With all of these meters, you can just crank the cal knob to full and just measure for lowest REV detected RF.

 

[C2]

And by doing that switching around you have a forward and reverse reading watt meter, not an SWR meter. You would have to do the converting of those readings to get SWR. Or, like those 'cross-needle' meters, you could calibrate an SWR scale. Lot of trouble though. That SWR scale is not linear...
- 'Doc

I would not call it a meter, but forward and reverse RF detector. When you have all your power forward and zero reverse...

Can't you find the lowest SWR by using only a reverse power reading meter?

 

[Captain Kilowatt]

Basically using a CB type meter to check SWR on 2m is like eating soup with a fork. You can do it, people will wonder WTF you are thinking, and in the end it is still not the right tool for the job regardless of the outcome.

 

[C2]

Spaghetti with a spoon? It's not nearly that frustrating.

 

[C2]

If one is so inclined... build your own swr meter for a few bucks...

VK5AJL - Build your own micro-stripline SWR meter - the only way to measure SWR.