SWR meter - Do it yourself project

[j5coat]

It works! It was a stupid mistake, and you already mentioned it. One of my connectors was not fully seating due to tight threads, it needed more than finger tight to make the connection. Thanks for all of your help and explanation rbcodell, i really appreciate it.

[rbcodell]

I'm glad I can help. I know its sometimes mystifying and hard to figure out on your own.
Dick

[neo__04]

Just a quick message to thank Alex for this great tutorial, Just finished my diy swr meter and it works a treat. Now.. to make my helical

Thanks again Alex

[fredz]

Hi All

Just finished my SWR meter and it seems to work great, thanks IB you da man

Noob question, how do you build a dummy load to test it?

Next stupid question, do you use the dummy load in place of the antenna to test the meter?

Results from a cloverleaf I built (thanks again IB) built for 1280 mHz

Freq ---------- VF ---- VR ----- P-- - SWR
1240MHZ - 2.743 - 0.452 - 0.165 -1.395
1280MHZ - 2.944 - 0.057 - 0.019 - 1.039
1320MHZ - 2.945 - 0.372 - 0.126 - 1.289

[rbcodell]

Hi All

Just finished my SWR meter and it seems to work great, thanks IB you da man

Noob question, how do you build a dummy load to test it?

Next stupid question, do you use the dummy load in place of the antenna to test the meter?

Results from a cloverleaf I built (thanks again IB) built for 1280 mHz

Freq ---------- VF ---- VR ----- P-- - SWR
1240MHZ - 2.743 - 0.452 - 0.165 -1.395
1280MHZ - 2.944 - 0.057 - 0.019 - 1.039
1320MHZ - 2.945 - 0.372 - 0.126 - 1.289

Correct. You can use a dummy load to test the meter setup. Ideally, with a dummy load you will get no reflected power; i.e., when you connect the dummy load to the left side and the transmitter to the right, the meter will read zero. However, in some cases, this won't happen, and that's usually the fault of the directional coupler not behaving ideally. This isn't a severe problem usually, because you can subtract the reflected voltage signal using the dummy load from what you get with the antenna to at least partially correct for this inaccuracy. Remember, that the main goal of testing is to reduce the reflected power to a minimum for best antenna performance, not actually to calculate SWR.

As far as dummy loads go, its best to purchase a real one. They are on ebay for just a few dollars each. I have made one in a pinch from a male sma connector, but its not advisable, especially at the highest frequencies (5.8 GHz).

Dick

[Pollux]

Hi,

good job for your antenna, 1.039 is a very good swr.

go back a few pages in this thread, I gave a link for a DIY dummy load.
At 1280 MHz, a selfmade dummy load should be ok if you use good non inductive resistors, but I can confirm what Rbcodell says... at 5.8 GHz, my (very carefully built) dummy load never passed under swr=1.20...

[Martin7182]

Hi guys,

I'm about to make some low power 50 ohm dummy loads. I have couplers with detachable loads and I wonder if it would be possible to use both ports simultaneously. So I want to terminate both ports with 50 ohm and use detectors on both ends at the same time.

Anyone knows where to find cheap 100 ohm low tolerance smd resistors? On Ebay I only see quantities of 100 or 400 and I just need 10 or so.
Otherwise, who's interested in getting such resistors? Spending a couple of $ is not the problem but I don't want to store hundreds resistors. Also don't want to throw them away unused.

Thanks,
Martin

[fredz]

Correct. You can use a dummy load to test the meter setup. Ideally, with a dummy load you will get no reflected power; i.e., when you connect the dummy load to the left side and the transmitter to the right, the meter will read zero. However, in some cases, this won't happen, and that's usually the fault of the directional coupler not behaving ideally. This isn't a severe problem usually, because you can subtract the reflected voltage signal using the dummy load from what you get with the antenna to at least partially correct for this inaccuracy. Remember, that the main goal of testing is to reduce the reflected power to a minimum for best antenna performance, not actually to calculate SWR.

As far as dummy loads go, its best to purchase a real one. They are on ebay for just a few dollars each. I have made one in a pinch from a male sma connector, but its not advisable, especially at the highest frequencies (5.8 GHz).

Dick

Hi Dick

Thank you ...... appreciate

I know this is a really noob .... dummy question, but are they called "dummy loads" or something else?

I did a search on eBay and most that came up looked like big heat sinks, did however find these,would they work for testing the SWR of my meter? coupler I am using is 800 - 2000 mHz

http://www.ebay.com.au/itm/SMA-male-...item4ab50af0d6

Thanks

Hi,

good job for your antenna, 1.039 is a very good swr.

go back a few pages in this thread, I gave a link for a DIY dummy load.
At 1280 MHz, a selfmade dummy load should be ok if you use good non inductive resistors, but I can confirm what Rbcodell says... at 5.8 GHz, my (very carefully built) dummy load never passed under swr=1.20...

Hi Pollux

Thanks, made another one and the SWR is really bad that's what I like about the meter is you can tell how well you either did or didn't do

[TurboCinqy]

Hi,

Today I tried to make the detectorprint but no succes.
Don't know why but there isn't almost any voltage output. Just 0.46VDC (0.6VDC in foward mode with -6dB attenuator -10db Coupler and 600mW Tx)
Tried another diode on the chip HSMS-286K but same issue.
Capacitor 103 ceramic. (10nF) resistor 1k.
Made it like IBC's image in the starters post.




This one has about 5cm Coax line RG316. and 20cm servo wire.


SWR meter.did an AutoCAD redraw of the scale. Used someone's file. To get it right.

[rbcodell]

Hi Fredz:
I looked on Ebay, and it looks like the ones you picked are the only ones I see available right now. Usually there are a lot of them. The trouble is they are only 1/8 watt, but that ought to be enough, especially if you don't leave the transmitter power on for a long time. They are all brass, and a lot of the heat should be conducted away from the resistor before they get too hot.
Dick