Loft mounted halfwave pipole RF saftey

[shorty]

These guys are ok to deal with, i've ordered from them before without problem, fast next day delivery as well.

http://www.ebay.co.uk/itm/RX-20-3-5-150 ... xyBotTY2DS

[bristolpirates]

These guys are ok to deal with, i've ordered from them before without problem, fast next day delivery as well.

http://www.ebay.co.uk/itm/RX-20-3-5-150 ... xyBotTY2DS

It needs at least 2 watts to show the SWR.

[halfwave]

Shorty:
Thanks for the heads up on the buyer.

Bristolpirates:
Does that mean I am scuppered with trying to get a swr reading as my transmitter is only 1watt?

Would this be the same for all swr metres, that they would require 2watts minimum to give a swr reading?

Sent from my Nexus 5 using Tapatalk

[s2000]

No they are all different. Have a look at this page, some of these will work with 0.5watts...

http://www.avair.com.tw/vswr.htm

[halfwave]

Ok, after spending all lunchtime looking on the net I think I may have found one:

SWR AVAIR AV-201 VSWR Meter
http://www.pjbox.co.uk/swr-avair-av-201-vswr-meter.html

From what I have managed to find to read about the AV-200 meter,
http://www.readbag.com/zcg-au-guides-av ... structions
as I cant find any user manual or info on the AV-201 meter.
It looks like the minimum power input is: 0.5 watt

By chance does anyone know what the difference between the AV-200 and the AV-201
is, as cant find any info to tell me anywhere.

[s2000]

Not too sure on the difference between them but the av201 looks good. It's actually the same one I have but under a different badge. Appears they may have made some improvements since I bought mine 20+ years ago, the meter will do 1kw! (for 30 seconds). My old sx200 is rated for 200w but will only handle 100W continuously (according to the manufacterers manual). Maybe they have uprated the rf coupler inside.

Its a very easy to use swr meter

[sde-1104]

The AV-20 will do the job

[teckniqs]

If you just want to see the SWR I'd just go for any old CB SWR meter because at least you can calibrate the FWD power to full scale before switching it over to see the REF power.
I don't think the Avair meter will give you the good enough results you require with 1w input, I have had one for about 10 years.

[halfwave]

The AV-20 will do the job

Hi,

Are you sure it will be OK for measuring a 1watt transmitter? As it states that the minimum input power needs to be 2watt.

Sent from my Nexus 5 using Tapatalk

[sde-1104]

The AV-20 will do the job

Hi,

Are you sure it will be OK for measuring a 1watt transmitter? As it states that the minimum input power needs to be 2watt.

Sent from my Nexus 5 using Tapatalk

Someone showed me one running half a watt before.

[teckniqs]

The meter uses the two needles crossed together for the SWR read out so with less than 2w the needles can't quite reach high enough to be able to cross and give you the correct SWR read out and it will just give you a rough idea.
....You will still be able to see if it's OK or not though by looking at the height of the REF needle compared to the FWD, so might as well just go for that one.

[MiXiN]

I have the Avair AV20 and regularly use it for testing 1W exciters.

It gives you a rough idea of the SWR at such a low power, and shows forward power, reflected power, and SWR all at the same time without any fiddling around with switches or knobs.

I'd go for that one, too.

I believe Avair copy the Diamond range of meters, hence others mentioning the SX-201.

[halfwave]

I think I am going to go for the Avair AV-201, as it's only a few quid more expensive
than the AV20 and it states that the minimum input is 0.5watt, so I can be certain
it will work with my 1watt TX.

The only think I need to do now is source a cable to take me from my transmitters
TNC female socket to the TX socket on the Avair AV-201 meter.
The back of which can be seen on this website below, where someone was selling their one.
http://www.gumtree.com.au/s-ad/lawnton/ ... 1112615546

I think somebody previously mentioned that the connection to the SWR Meter would be
a PL259 male that I would require.

I expect that I would need a TNC male plug to PL259 male cable.

I have had a look on-line and have found a cable below, but just want to make sure
that the cable and connectors will be compatible and work with the above:

Cable 3FT TNC male plug to UHF PL259 male KSR400/RG8 RF Pigtail jumper cable
http://www.ebay.co.uk/itm/Cable-3FT-TNC ... 3641.l6368

Could someone advise if this cable is correct to use.

I think I should be able to use the following adapter to take my existing TNC male connection, which is on the end of my aerial coax cable, into the ANT socket on the back of the SWR meter.

http://www.amazon.com/coaxial-adapter-f ... B00CXNO224


Things would certainly be easier if all connections were the same type as standard LOL.

[s2000]

You can make the leads up yourself if you prefer but if you're not used to soldering/crimping etc.. then I would do the following...

Buy yourself some good quality pl259 leads for the lengths you require and get yourself some tnc male to so239 adaptors. The reason for this is because most other gear you buy e.g transmitters, swr meters, antennas etc use the so239 socket as standard so you will be able to use the same leads if you upgrade.

Please bear in mind if you are running a long lead to your aerial it's best to get a good quality lead with thick cable e.g rg213 etc.. If you use rg58 leads and the length is long you will loose quite a bit of your transmitter power in the lead (as the cable is lossy).

Also make sure everything is 50 ohms impedance.

[halfwave]

s2000:

Thanks for the information with regards to the cables and connectors.

I have now orderd a RG213 Patch lead (50 ohms) with 2 PL259 Connectors, and after spending
a couple of hours trawling Google, I have also found and ordered the correct adapters to take
the leads back to my transmitter and aerial. I also ordered the Avair av-201 SWR meter too.

Thanks again for everyone's help, it's much appreciated.

[bristolpirates]

The meter uses the two needles crossed together for the SWR read out so with less than 2w the needles can't quite reach high enough to be able to cross and give you the correct SWR read out and it will just give you a rough idea.
....You will still be able to see if it's OK or not though by looking at the height of the REF needle compared to the FWD, so might as well just go for that one.

I get no reading at all on the second needle out of mine with a watt, just the fwd power. It might get going at over a watt but still under 2 watts, but I've never had a chance to find out. Definitely works with 25 going through, so it's not broken.

[radionortheast]

measured my aerial in the loft swr is 2 the peak is down on 77mhz where its 1.2, must be the effect of the aerial touching something (ie the roof slates)

might be best if you where going to be doing this leaving a gap 1 foot at the top to avoid detuning the aerial the other idea is shortening the elements, perhaps using a shorter aerial is better in a loft?

[halfwave]

Hi,

Finally have got my patch leads, connectors and SWR meter.
So hooked it up and unfortunately when I try to calibrate it by turning
the knob the needle will only go half way across the meter and does not
get to the right hand side calibration point.
(So I guess that 1 watt is not enough power).

So as I could not measure the SWR like that I just took the Forward and then Reflected power
readings, which where as below:

Pfor: 1.0 watt
Pref: 0.1 watt

Then went to this site: http://rfcalculator.mobi/vswr-forward-r ... power.html
and entered the figures into the online calculator and it showed that my SWR would be: 1.924951
Is this bad? as I read somewhere that you should try and get it to under 1.5.
So I may have to look at re-building a new Dipole (or flowerpot antena).

BTW.
Does anyone have a good tutorial on building a 1/2 wave dipole?
FYI. I made my current diplole by followed the instructions from this tutorial:
http://www.doityourselfchristmas.com/wi ... ntenna.pdf

On a side note, I also found a link to an Excel Calculator that someone has written that also calculates SWR
along with a whole host of other calculators that may be of interest to some of you too.
http://www.birdrf.com/en/Resources/TechnicalTools.aspx

[teckniqs]

That was why at first I suggested just a standard SWR meter with calibration dial for use at that power.

[halfwave]

That was why at first I suggested just a standard SWR meter with calibration dial for use at that power.

Yes, I should have gone with what you suggested

I will probably get a 7 watt transmitter soon anyway
so at least it will work correctly then