Icom: IC746 VHF Band not reaching 100W output

[weccwwe]

Hi all,

I just purchased from a radio shop a used IC746 base transceiver, Looks like everything is functioning normally.

I am trying to figure the power output from the VHF band, between 144 - 148, it fluctuates from 100 watts down to 20 watts.

144.070 - 100 watts
145.070 - 40 watts
146.050 - 20 watts
146.390 - 20 watts
147.050 - 20 watts
147.550 - 50 watts
147.990 - 100 watts

I am transmitting in both FM & RTTY and it's the same, power settings are max, and mic gain adjusted.

Now I am used to my mobile UHF/VHF units, when they all say 50 watts, they are all actually at 50 watts throughout the whole band.

Is something wrong with this unit? I have gone through the manual, but am I missing something? With the power and mic gain settings the same, HF is 100watts constant throughout all bands.

I have also reset the CPU to default, no help.

Regards

 

[krokus]

Are you testing by transmitting into a dummy load?

 

[a417]

If you are not transmitting into the aforementioned dummy load for testing, what are you transmitting into? Is it rolling back due to high SWR?

 

[weccwwe]

Hi good morning

I am testing with my existing inline antenna 200 watt needle tester,

Onto my existing jpole, highest existing swr throughout the 2m is 1.4.

My other handhelds and mobiles use the same exact setup when I connect them.

No other 2m radio is displaying the same results as this ic746 using the same antenna and tester set up

 

[krokus]

Do you have a VNA? Sweep your antenna and coax, to make sure there is not another issue.

 

[weccwwe]

Great thank you, I don't have one but a friend of mine does, will take another look at my current antenna setup

 

[weccwwe]

Hi Krokus,

Quick update, Finally had a chance to investigate my antenna setup more, Looks like there is an issue with the jpole itself, that my inline power/swr meter didn't show, but it showed up on an Analyzer.

Off to dxengineering website to looks for a decent and decently priced uhf/vhf base antenna now........

Thank you for recommending to take another look at my antenna setup.

 

[techman210]

Friends don’t let friends install J-Poles.

or Ringo Rangers😀

 

[weccwwe]

Lololol

 

[krokus]

Off to dxengineering website to looks for a decent and decently priced uhf/vhf base antenna now........

Glad to hear that you found the problem. Do you know what you want as the replacement? (Or start another thread on that topic.)

 

[weccwwe]

Called DXengineering, after consulting with a sales guy, recommended that I replace the RG213 with LMR400 because of the crazy high db (>4.4) that he calculated with 75' of cable that I require, and a Diamond X300A

Input, Krokus?

 

[prcguy]

LMR400 has less loss than RG-213 and you should notice better overall performance using 75ft of cable. But that has nothing to do with your radio showing less power on some freqs as others. It could very well be your radio is folding back the power due to sensing a bad match but you will never know until you put a known good 50 ohm load on the radio and test over the same frequencies.

Called DXengineering, after consulting with a sales guy, recommended that I replace the RG213 with LMR400 because of the crazy high db (>4.4) that he calculated with 75' of cable that I require, and a Diamond X300A

Input, Krokus?

 

[weccwwe]

I should buy a dummy load first?

 

[prcguy]

I would recommend thoroughly testing the radio separate from the antenna to make sure its working, or not. You already have a wattmeter so borrow, buy or steal a dummy load and find out if the radio has a problem. A new antenna won't do much good if the radio is broken.

I should buy a dummy load first?

 

[krokus]

I would recommend thoroughly testing the radio separate from the antenna to make sure its working, or not. You already have a wattmeter so borrow, buy or steal a dummy load and find out if the radio has a problem. A new antenna won't do much good if the radio is broken.

They swept the antenna with a VNA, and found the problem.

 

[krokus]

Called DXengineering, after consulting with a sales guy, recommended that I replace the RG213 with LMR400 because of the crazy high db (>4.4) that he calculated with 75' of cable that I require, and a Diamond X300A

Input, Krokus?

Those will make a major difference, for the better.

I would still borrow a dummy load, to test the transmitter.

 

[weccwwe]

Thank you guys for your help

I could not find a dummy load for my personal use at home, but the local radio speed shop helped me out by testing the radio on their bench dummy load this morning when I brought it in for free.

The radio is functioning perfectly and as expected

I ended up purchasing a new tram 1481 from
the shop I was at. The service person also said that unless I have an issue with the rg213, I do not need to replace it with lmr400.

 

[prcguy]

Great to hear the radio is ok and that paves the way for your new antenna and new more distant contacts.

Thank you guys for your help

I could not find a dummy load for my personal use at home, but the local radio speed shop helped me out by testing the radio on their bench dummy load this morning when I brought it in for free.

The radio is functioning perfectly and as expected

I ended up purchasing a new tram 1481 from
the shop I was at. The service person also said that unless I have an issue with the rg213, I do not need to replace it with lmr400.

 

[weccwwe]

Hi Guys,

Just a quick final update. I finally installed this Tram 1481 antenna. Didn't realise that this thing is 17 feet tall!!! Anyways, It definitely was worth the upgrade to the homemade JPole. 1:1 throughout the whole band. The IC746 is now pinned and 100Watts throughout the whole VHF. I pinged a repeater 120kms (74miles) away! There was static, but clear enough to hear the call sign. I stuck with the existing 75' of RG213. Local radio speed shop guy was right, no need to switch to LMR400 in my situation.

Thank you guys again for all your assistance.

 

[paulears]

People forget that reception and transmission performance is the entire chain end to end.you get gain from some elements and loss from the other. the arguments start once you try to balance cost with success! 3dB to 6dB at the antenna might cost one figure, and 3dB in the cable another. Both is best, but at what price. The price part also links to performance. The question is what do you want. For my business, VHF marine is most important, but distance is not. My building has two floors and a roof above me. My antennas are on a ground mounted pole and the top antenna is 3m above ground. I get coverage east to around one mile offshore, and about half a mile north and south. West is zero due to the building. This is for me fine. My UHF repeater is on my home north and it’s slightly noisy but fine, and my local ham repeaters are half a mile due east so they’re great. To get my antennas able to look west means a tower and groundwork’s that would cost at least two grand. Pointless. If you need maximum system gain the the antenna and the cable need sorting. A good antenna and lossy cable could be fixed. It’s just money. My situation is lots of money so I’m not doing it. Could you live with that extra 3dB loss? Probably.