SWR Meter

[mickywillis]

Evening all,
Having issues with connecting a Quark QK-A015-TX VHF Aerial Splitter to an Icom MA500TR AIS Transponder.
When connected via the splitter, after an initial transmission of the AIS signal (indicated by the green LED on the rear of the splitter) the Icom flashes up a warning " Antenna Malfunction High VSWR" If I reset all the equipment, the same problem occurs again. The Icom has a diagnostic screen and when displayed, the antenna test shows NG (no good!)
If I connect the Icom directly to the VHF aerial, it all works OK, no errors or faults detected. I have a Cobra fixed VHF and this transmits and receives OK when connected to the masthead VHF aerial ( a Vtronix Hawk, fitted about 6 years ago)
Could possibly be an issue with the connecting patch leads, so need to test those or replace them.
If these dont prove to resolve the issue, I guess that I need to get a SWR meter and do some fault finding?
Is it possible or OK to use a SWR that was originally designed to be used with CB or Amateur radio equipment? Something like this: Trans Swr And Power Meter? Cb Radio/ Ham Radio? | eBay
If not, can you direct me to a suitable unit please?
Thanks.

 

[st599]

If it's a CB SWR meter it's tuned for 27MHz, nowhere near 160MHz.
VHF 2m band is closer, but still not ideal.

You can get a great miniVNA for not much money for testing RF kit. It'll give you a frequency vs SWR plot but it may not have enough oomph to switch the device to the AIS path.

The device says it fails to VHF transmission - so is there enough voltage? Is the power of the AIS high enough to switch the device? Is the AIS cable damaged?

 

[Andrew_Trayfoot]

I have a marine band swr metre you can borrow if you are in the vicinity of Dorset

 

[Martin_J]

I use a Diamond SX-200 which covers 1.8-200 MHz so nicely covers the 156MHz marine VHF frequencies (and as it happens the HF frequencies as well)

They're sold at Nevada Radio, just up the road from your sailing area..

Diamond SX-200 - Nevada Radio

if you're near Southsea then let me know and you can try it out. I should be able to find it and a few good patch cables, antennas etc...

 

[Martin_J]

If you have good power to the splitter then as you're expecting, you will likely find either a shorting strand or a high resistance joint in a patch lead..

It's nice to prove out the tester whilst the fault is present, then see the difference in what it shows with the working setup afterwards.

 

[Skylark]

Evening all,
Having issues with connecting a Quark QK-A015-TX VHF Aerial Splitter to an Icom MA500TR AIS Transponder.
When connected via the splitter, after an initial transmission of the AIS signal (indicated by the green LED on the rear of the splitter) the Icom flashes up a warning " Antenna Malfunction High VSWR" If I reset all the equipment, the same problem occurs again. The Icom has a diagnostic screen and when displayed, the antenna test shows NG (no good!)
If I connect the Icom directly to the VHF aerial, it all works OK, no errors or faults detected. I have a Cobra fixed VHF and this transmits and receives OK when connected to the masthead VHF aerial ( a Vtronix Hawk, fitted about 6 years ago)
Could possibly be an issue with the connecting patch leads, so need to test those or replace them.
If these dont prove to resolve the issue, I guess that I need to get a SWR meter and do some fault finding?
Is it possible or OK to use a SWR that was originally designed to be used with CB or Amateur radio equipment? Something like this: Trans Swr And Power Meter? Cb Radio/ Ham Radio? | eBay
If not, can you direct me to a suitable unit please?
Thanks.

The one you’ve linked looks to be from the cheap end of the market but I’m sure that it would meet your needs. It’s likely inaccurate and not designed for vhf but as a crude test of fault finding, it’s fine.

I’ve always preferred twin meter displays and had one of these for about 40 years.
Vintage Albrecht SWR-25 SWR and RF Power Meter 150Mhz | eBay

More recently, Nano Vector Network Analysers have become widely available for pennies. Years ago these would cost thousands and only be found in laboratories. They take a little more thought and effort to setup but they will give a graph of SWR against frequency. Here’s a typical 4 inch screen version
SEESII NanoVNA-H Vector Network Analyzer 10KHz-1.5GHz MF HF VHF UHF SD Card Slot | eBay

Your best option is to borrow something as you’ll probably only use such a device once. Where are you/boat based?

 

[st599]

More recently, Nano Vector Network Analysers have become widely available for pennies. Years ago these would cost thousands and only be found in laboratories. They take a little more thought and effort to setup but they will give a graph of SWR against frequency. Here’s a typical 4 inch screen version
SEESII NanoVNA-H Vector Network Analyzer 10KHz-1.5GHz MF HF VHF UHF SD Card Slot | eBay

But will the VNA provide enough power to cause the switch to activate. It's normal position is connecting the VHF to the antenna. It's expecting a watt or more from the AIS. I'd the VNA doesn't switch it, you'd expect a huge insertion loss (and VSWR).

 

[Skylark]

But will the VNA provide enough power to cause the switch to activate. It's normal position is connecting the VHF to the antenna. It's expecting a watt or more from the AIS. I'd the VNA doesn't switch it, you'd expect a huge insertion loss (and VSWR).

Don’t know, but you’re probably right. The way I read the OP, nothing, radio nor ais, is getting out. First check should always be the newly fitted items, patch leads and splitter.

 

[oldgit]

Recently had some trouble with a Digital Yacht AIS system unable to receive any signals , it was almost certainly a failure of the matching Digital Yacht antenna switch.
It was TX ing OK !
Being unable to even discover the location of the switch , simply removed it from the system and connected the AIS transponder directly to a separate antenna.
The transponder box has a female usb lead which allows you, via a laptop and software , not only to diagnose faults find but to read the SWR between transponder and aerial.
Initially tried to use a PL to BNC adaptor to check ................... the SWR reading was dreadful.
Fitting a proper soldered BNC plug to the end of the aerial cable corrected the problem and the system is now working properly.

 

[Poey50]

I bought this one and it does the job.

Moonraker SWR-270 Dual Band SWR/Power Meter VHF UHF 120 to 500MHz 5060080572106 | eBay

 

[Refueler]

First ... the splitter will cause the SWR meter the heeby-jeebys ...... why ?

Because the splitter causes antenna link to sever depending on which is TX'g at that time. Second - the splitter circuitry ...

I have splitter between my AIS and VHF to antenna. If I have antenna direct to VHF - Antenna test on the VHF is good and passes. Fit splitter and antenna check fails everytime.
I have an SWR and Power meter specifically for VHF band .... fine when splitter is removed and antenna direct to VHF ... but connect splitter and it fails.
Therefore my check is to call up a pal on low power who has his boat 2km from me in the Yacht Club .....

 

[Alex_Blackwood]

Evening all,
Having issues with connecting a Quark QK-A015-TX VHF Aerial Splitter to an Icom MA500TR AIS Transponder.
When connected via the splitter, after an initial transmission of the AIS signal (indicated by the green LED on the rear of the splitter) the Icom flashes up a warning " Antenna Malfunction High VSWR" If I reset all the equipment, the same problem occurs again. The Icom has a diagnostic screen and when displayed, the antenna test shows NG (no good!)
If I connect the Icom directly to the VHF aerial, it all works OK, no errors or faults detected. I have a Cobra fixed VHF and this transmits and receives OK when connected to the masthead VHF aerial ( a Vtronix Hawk, fitted about 6 years ago)
Could possibly be an issue with the connecting patch leads, so need to test those or replace them.
If these dont prove to resolve the issue, I guess that I need to get a SWR meter and do some fault finding?
Is it possible or OK to use a SWR that was originally designed to be used with CB or Amateur radio equipment? Something like this: Trans Swr And Power Meter? Cb Radio/ Ham Radio? | eBay
If not, can you direct me to a suitable unit please?
Thanks.

From that you know that the VHF, AIS transponder and antenna are all working. That leaves the splitter or the leads. Double check and double check your leads. Do the units work if individually connected to the splitter? Try all that first before SWR meters!
Edit:- See Refueler's comments.

 

[Refueler]

I think people are forgetting that the AIS Tx will be low power .. and it will be Tx'g frequently causing the splitter to close of VHF ..... many SWR meters fail with such low power ... plus a lot of retail meters need a signal of more than a few millisecs ...

I was talking to the dealer who supplied my gear and he was honest that his meter just to test the AIS alone - was an expensive industry meter to be able to read the low AIS power and its short Tx time.

 

[Martin_J]

This use of an SWR meter was not intended to test the output transmission power of the AIS or to try to catch it's brief transmissions.

I would usually use a known working transmission source with a known carrier power as the input device.. It would be connected to the VHF input and SWR tests done at each connection, followed by using the same source on the AIS input to the splitter.

Usually the splitter will accept up to 25W on the VHF input and 12.5W on the AIS input. It would be easy to put a constant 25W into the VHF input and perhaps (after checking the active splitter specification) a constant 5W into the AIS input for test.

I would not expect to connect a power/SWR meter into either the AIS feed into the splitter or into the Antenna side of the splitter and hope to see what it could measure in the twenty'odd milliseconds that the AIS transponder would transmit for.

(Edit - So I agree with Refueler in that we don't expect to easily capture power or SWR from a very brief AIS transponder transmission).

 

[mickywillis]

I have a marine band swr metre you can borrow if you are in the vicinity of Dorset

Thank you Andrew, but based in Langstone Harbour, near Portsmouth, Dorset a bit far I'm afaraid!

 

[mickywillis]

I use a Diamond SX-200 which covers 1.8-200 MHz so nicely covers the 156MHz marine VHF frequencies (and as it happens the HF frequencies as well)

They're sold at Nevada Radio, just up the road from your sailing area..

Diamond SX-200 - Nevada Radio

if you're near Southsea then let me know and you can try it out. I should be able to find it and a few good patch cables, antennas etc...

Martin, Thank you for your kind offer, but looking at the comments, it seems that teh SWR meter may not detect the issue with the AIS Tx High VSWR indication? However, it may be a good idea to check the SWR of the existing setup without the AIS Tx/Rx in situ, just to ensure the setup is matched OK, I may take you up on your offer of a loan! But changing patch leads as a first attempt as they are easily replaceable and not too expensive.

 

[mickywillis]

The one you’ve linked looks to be from the cheap end of the market but I’m sure that it would meet your needs. It’s likely inaccurate and not designed for vhf but as a crude test of fault finding, it’s fine.

I’ve always preferred twin meter displays and had one of these for about 40 years.
Vintage Albrecht SWR-25 SWR and RF Power Meter 150Mhz | eBay

More recently, Nano Vector Network Analysers have become widely available for pennies. Years ago these would cost thousands and only be found in laboratories. They take a little more thought and effort to setup but they will give a graph of SWR against frequency. Here’s a typical 4 inch screen version
SEESII NanoVNA-H Vector Network Analyzer 10KHz-1.5GHz MF HF VHF UHF SD Card Slot | eBay

Your best option is to borrow something as you’ll probably only use such a device once. Where are you/boat based?

Based in Langstone Harbour, South Coast. The Albrecht one you link to is only rated to 150Mhz, would that be OK for Marine VHF as I understand Marine transmits at about 156Mhz?

 

[Martin_J]

Martin, Thank you for your kind offer, but looking at the comments, it seems that teh SWR meter may not detect the issue with the AIS Tx High VSWR indication? However, it may be a good idea to check the SWR of the existing setup without the AIS Tx/Rx in situ, just to ensure the setup is matched OK, I may take you up on your offer of a loan! But changing patch leads as a first attempt as they are easily replaceable and not too expensive.

The Power/SWR meter will be able to test out both paths through the active splitter that you have... It's what it's designed for.

It would only take a couple of minutes to test out at 25 Watts through the VHF input and then 5 or 6 Watts through the AIS input which will prove out both patch cables you have going into the splitter as well as the cable from there to the masthead antenna.

It's quicker to use it for all that than it is to describe... The offer is still there.

Thinking about it again.... the issue could be in the feed to the antenna or the antenna itself. It's only the fact that the AIS is pointing out that there is an issue that brings it to light.

Did you try the AIS transponder connected direct to the antenna cable to see if that's successful..? There may even be more than one issue hence the Icom reporting an issue at one point


As to the Albrecht meter. You don't know it's provenance and AIS uses channels 87 and 88 (161.975MHz and 162.025MHz) which is above its reliable range. You might get an indication of SWR but you really would be better off waiting and getting something that really covers the range you're always going to want to test.

 

[Martin_J]

How about a quick easy way to connect the AIS output direct to the antenna feed cable whilst keeping the original patch cable in place...

Put an SO239-SO239 connector in place of the splitter.. They're only a few pounds and are useful to have in the spares kit..




Then see if the SWR alarm led lights during transmission.

 

[mickywillis]

The Power/SWR meter will be able to test out both paths through the active splitter that you have... It's what it's designed for.

It would only take a couple of minutes to test out at 25 Watts through the VHF input and then 5 or 6 Watts through the AIS input which will prove out both patch cables you have going into the splitter as well as the cable from there to the masthead antenna.

It's quicker to use it for all that than it is to describe... The offer is still there.

Thinking about it again.... the issue could be in the feed to the antenna or the antenna itself. It's only the fact that the AIS is pointing out that there is an issue that brings it to light.

Did you try the AIS transponder connected direct to the antenna cable to see if that's successful..? There may even be more than one issue hence the Icom reporting an issue at one point


As to the Albrecht meter. You don't know it's provenance and AIS uses channels 87 and 88 (161.975MHz and 162.025MHz) which is above its reliable range. You might get an indication of SWR but you really would be better off waiting and getting something that really covers the range you're always going to want to test.

Martin, The Icom AIS unit works fine when connected directly to the VHF aerial coax PL259 connector. It transmits OK (seen on AIS Vesselfinder) and doesn't report the High VSWR issue when running for at least 15mins. I've ordered a couple of new patch leads and will try these first. The vendor of the VHF splitter isnt being very helpful and the manufacturer (Quark) hasn't replied to my emails for assistance.