Icom IC-F5021 35W output instead of 50W

[rabrol]

Hi folks.

I picked up an F5021 that seems in good shape, other than the output power appears to be limited to 35W rather than 50W.
Anyone know what would cause that problem, and what might the troubleshooting steps be? I have seen the same issue on other commercial equipment from time to time. Would be nice to know what causes it and if it is easily fixable?

 

[cmdrwill]

Could be that the frequency programmed may have a TX power restriction. Can you "read" the radio without making ANY CHANGES? Be sure to SAVE the radio's existing programming, and save that in a safe place.

 

[rabrol]

No, not a programming restriction. It is a codeplug I compiled.
However I am currently wondering if it could be an issue with my SWR/Power meter (a Diamond branded unit). I tried a new 50W radio on the meter, and it showed 35W as well!

 

[merlin]

No, not a programming restriction. It is a codeplug I compiled.
However I am currently wondering if it could be an issue with my SWR/Power meter (a Diamond branded unit). I tried a new 50W radio on the meter, and it showed 35W as well!

That clearly suggest it is your watt meter at fault. For VHF/UHF you really need a good watt meter made for the higher frequencies. I am guessing your Diamond is for LF/HF amateur use.

 

[12dbsinad]

Check the specs of your meter, some of them are only for HF use.

 

[rabrol]

Check the specs of your meter, some of them are only for HF use.

It is supposed to include the VHF band (SX-200 model, 1.8-200MHz), and has been showing that my radios are outputting 50W up until this week. Had it 4 or 5 years. Maybe time to replace?

 

[rabrol]

It is supposed to include the VHF band (SX-200 model, 1.8-200MHz), and has been showing that my radios are outputting 50W up until this week. Had it 4 or 5 years. Maybe time to replace?

Actually, just had a look, it is the SX-400, VHF / UHF : 140-525 MHz.

 

[kb5udf]

What is the voltage going into the radio under load? (while transmitting). Some radios will t/x decreased power if voltage sags.

 

[mmckenna]

...has been showing that my radios are outputting 50W up until this week. Had it 4 or 5 years. Maybe time to replace?

OK, wait, walk me through this again.

This Icom is new to you, right?
Do your other radios show correct power output?
Are you testing into a 50Ω dummy load, or into an external antenna
-Is it possible something changed with your antenna or feedline? Most good radios have a circuit that senses high SWR and will automatically throttle back power if it senses it getting too high.

 

[rabrol]

This Icom is new to you, right?
Do your other radios show correct power output?
Are you testing into a 50Ω dummy load, or into an external antenna
-Is it possible something changed with your antenna or feedline? Most good radios have a circuit that senses high SWR and will automatically throttle back power if it senses it getting too high.

Yes, the Icom is new to me here, but could be a 10 year old radio.
Testing has been into an external antenna. Your comments reminded me that I had switched the antenna earlier this week to one with a slightly different tuning. So I went back to my original antenna and tested again.

Nothing changed in the feedline.
Tested 2 radios - one looks like it throwing the full power out, the other appears stuck at 30W or so. I guess that means the original question remains. What is happening to the last 20W of output?

As for a dummy load - still have not acquired one, but it is approaching the time I did!

 

[mmckenna]

A good 50Ω load is a useful tool for troubleshooting.

It's entirely possible that the new radio had the RF output turned down by the previous owner. There are applications where more RF power isn't desired. It may have been a limitation on the license. Sometimes we'll do it with our mobiles to help extend the life. In reality, that 20 watts isn't making a big difference in your coverage.

Also,
Check your DC power connections. Not sure if Icom is still using the glass AGC type fuses in their power leads, but if they are, they are known to have some voltage drop across them. As your DC voltage goes down, so will the RF output. Check any crimp connectors to make sure they are properly crimped.

With used radios, you never know what you are getting. May have been an intentional turn down of the RF power. Could have been someone screwing around with the alignment and not knowing what they are doing. Could be a bad antenna jack. Could be a broken solder joint on the back of the connector.
Having the right test equipment is important. It may be worth the money to send it in for check up. If it's working correctly, other than the low power output, it may be just fine.
Professionally, however, I'd suspect that something is either wrong with the radio, or someone made adjustments to it. Unless I knew for sure that the person who did that had the right test equipment, I'd probably spend some time realigning the entire radio just to make sure it's working to spec and not going to interfere with other users.

 

[rabrol]

A good 50Ω load is a useful tool for troubleshooting.

It's entirely possible that the new radio had the RF output turned down by the previous owner. There are applications where more RF power isn't desired. It may have been a limitation on the license. Sometimes we'll do it with our mobiles to help extend the life. In reality, that 20 watts isn't making a big difference in your coverage.

Also,
Check your DC power connections. Not sure if Icom is still using the glass AGC type fuses in their power leads, but if they are, they are known to have some voltage drop across them. As your DC voltage goes down, so will the RF output. Check any crimp connectors to make sure they are properly crimped.

Thanks for these tips for looking into the problem. If power output is turned down, is that performed electronically (via software), or via a physical manipulation 'under the hood'?

The DC output is coming from a Samlex 13.8V 23 amp supply, which is feeding into a distributor, which in turn supplies 4 or 5 radios with power. With no other radios connected, other radios are showing the full (or close to full) output. With this one connected, the RF output is lower.
I can look into the actual voltage at the radio, but haven't as yet, since other radios are outputting fine when connected via the same connector (also with no other radios connected to the distributor).

Having the right test equipment is important. It may be worth the money to send it in for check up.

Professionally, however, I'd suspect that something is either wrong with the radio, or someone made adjustments to it. Unless I knew for sure that the person who did that had the right test equipment, I'd probably spend some time realigning the entire radio just to make sure it's working to spec and not going to interfere with other users.

I only have very simple equipment here, so I expect I would not be able to align the radio correctly. What tools / equipment are needed to perform an alignment? I guess something a lot more accurate than a Diamond SWR / Power meter!!!

 

[mmckenna]

Thanks for these tips for looking into the problem. If power output is turned down, is that performed electronically (via software), or via a physical manipulation 'under the hood'?

It's in software. And while I can appreciate the idea of fixing/adjusting it yourself, the alignment procedures to do it correctly are not as simple as "adjust until it reads 50 watts".

I only have very simple equipment here, so I expect I would not be able to align the radio correctly. What tools / equipment are needed to perform an alignment? I guess something a lot more accurate than a Diamond SWR / Power meter!!!

Well, my concern is that if the radio has been adjusted from factory specs by an unknown person, you should suspect that it was not done correctly. To do that, you need a service monitor and some additional tools. A new service monitor runs in the $40,000 range. Used, you'd be looking in the $2000 range at least to get anything reliable.

But, for just adjusting the power output, you'd probably only need a reliable power meter. I'd not trust a wide banded Diamond meter like that. Usually in the industry something like a Bird 43 with the correct slugs would be used. You'd need a 50Ω dummy load, one in the 100 watt range would be a good idea.
You'll also need a digital ammeter with at least a 20 amp capacity.
That should get you close.

A Bird 43 with a good selection of slugs and a 100 watt 50Ω load is a pretty hand setup.

 

[12dbsinad]

Yeah, connect it into a dummy load for testing purposes. What is the VSWR when connected to said antenna(s)? Those radio's will start to fold back TX power if the match if off more than it wants to see to save the PA. If you have high VSWR than it's possible that is what's happening. If that's the case running it into a 50 ohm load should reveal a perfect match and the radio will put out full output power.

 

[rabrol]

Yeah, connect it into a dummy load for testing purposes. What is the VSWR when connected to said antenna(s)?

Yes I'm glad that radios do that. The VSWR was 1.4:1 on the frequency I was testing. I don't believe that would result in the radio pulling back any power, although I'm not honestly sure what SWR that kicks in at. Do you happen to know?

 

[mmckenna]

Yes I'm glad that radios do that. The VSWR was 1.4:1 on the frequency I was testing. I don't believe that would result in the radio pulling back any power, although I'm not honestly sure what SWR that kicks in at. Do you happen to know?

Not sure about Icom, but it's usually around 2.5 or 3.

Unlikely an SWR of 1.4 is causing it to fold back on the power. If your SWR meter is accurate.