SWR & ANTENNA ANALYZERS

I am venturing into the world of Ham radio (Covid19 permitting) and I am fascinated by the diy construction of aerials of which I have had some success with on 27mhz. I am now struggling with 2m and 70cm. I have followed some designs and instructions from t'internet and I can not get them to slot straight in to below 1.5:1 as they do but I wonder if it's a basic ignorance. I started to think about it a bit deeper and realise there might be problems because of measuring equipment - i.e. SWR meter which works perfectly on 27mhz - is it compatible with 2m and 70cm measurement? Do I need an antenna analyser? Might seem simple things to the amateur users but since I can't get to join the local club because of the virus I wonder if I can get any response on here. I don't mind a bit of mickey taking and the pointing out of the obvious if I can benefit from the replies...

Blue Boy wrote:

I am venturing into the world of Ham radio (Covid19 permitting) and I am fascinated by the diy construction of aerials of which I have had some success with on 27mhz. I am now struggling with 2m and 70cm. I have followed some designs and instructions from t'internet and I can not get them to slot straight in to below 1.5:1 as they do  but I wonder if it's a basic ignorance. I started to think about it a bit deeper and realise there might be problems because of measuring equipment - i.e. SWR meter which works perfectly on 27mhz - is it compatible with 2m and 70cm measurement? Do I need an antenna analyser? Might seem simple things to the amateur users but since I can't get to join the local club because of the virus I wonder if I can get any response on here. I don't mind a bit of mickey taking and the pointing out of the obvious if I can benefit from the replies...

I use one of these (mine is the Rigexpert AA-30 model for CB / 27 mhz frequencies). There are various models for different frequency-ranges and they are very easy to use. You simply connect it to the antenna co-ax, type in the frequency and then read the SWR (and other Info) on the screen. You can also connect the analyzer to a PC by USB cable and view the results there. Software is supplied with the analyzer but (depending where you buy it from) you may have to purchase the USB cable separately. These are usually available from any Ham radio shop and / or Ebay.....prices vary depending on model. See video at link below for a full demo.

http://www.mixw.co.uk/

Video of AA-30 Demo:
https://www.youtube.com/watch?v=GGNd6cTohVU

I have a avair vswr meter that covers 0 - 200mhz I don't use 70cm much apart from the odd repeater but that's with a bought colinear so pre tuned .

Analysers are handy but costly for a good one . I have survived without one though .

73 , Matt

If you are using a SWR meter designed for 27Mhz it will not be accurate on 2/70.

73's Gary.

SWR meters usually have a frequency range. Mine does 0-30MHz and has a switch to then do VHF/UHF (100-500MHz, from memory) on the other range.

However, analysers are SO much more useful...and a little NanoVNA connected to a laptop with something like NanoVNA Sharp is an awesome little tool that will cost less than a good SWR meter!

Blue Boy wrote:

I can not get them to slot straight in to below 1.5:1 as they do  but I wonder if it's a basic ignorance. I started to think about it a bit deeper and realise there might be problems because of measuring equipment - i.e. SWR meter which works perfectly on 27mhz - is it compatible with 2m and 70cm measurement?

No. Different types of resistor (carbon, metal film, wirewound etc) operate differently over a different range of frequencies. Your bog standard carbon resistor used in a CB meter can halve in impedance when it gets up to VHF, a 1k Ohm at 27MHz could be as little as 500 Ohms at 2m, which will skew the readings and CB SWR meter manufacturers aren't going to put in the expensive wirewound ones.

Quote :

Do I need an antenna analyser?

To put it simply, yes. One thing it can do which your SWR meter can't is measure outside of the range of frequencies your radios can transmit on which is invaluable for finding out just where something is resonant that is a fairly high SWR on the bands you want to use it on.

You don't need to spend loads of money on one though. There's loads of nanoVNA ones for sub £50 with a nice graphical display which will do the job.

43CT016 wrote:

SWR meters usually have a frequency range.  Mine does 0-30MHz and has a switch to then do VHF/UHF (100-500MHz, from memory) on the other range.

However, analysers are SO much more useful...and a little NanoVNA connected to a laptop with something like NanoVNA Sharp is an awesome little tool that will cost less than a good SWR meter!

I've got the nano VNA Jeff, best £30 quid I've ever spent!!!

Excellent - thanks for all the info back. I can be quite focussed now on what I want to do. Nice to have the support - thanks again...

GaryWilson wrote:

I've got the nano VNA Jeff, best £30 quid I've ever spent!!!

Yeah, I had an older MFJ analyser too, but it topped out at about 170MHz for VHF.  No UHF at all, so useless for 70cm and our CB band here which is 477MHz.

So faced with spending fortunes on a RigExpert 600, or $100 on a NanoVNA, the choice was simple.

Particularly useful when playing with antennas that have a matching section, because you can see not just the impedance figure, but what it's made up of.