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Author Topic: Icom IC-718 USB XMIT promblem?  (Read 3203 times)
CLEBOT
Member

Posts: 100




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« on: July 10, 2006, 01:53:11 PM »

Good morning,
I recently acquired an Icom IC-718 transceiver (with MARS mod), and MFJ-993B Intellituner.
I have just become affiliated with MARS and am participating in the MARS nets (made my first HF contact 2 days ago on the MARS net). Anyhow, not wanting to miss my first check-in with the net, I fired up my transceiver and tried to make contact. I dialed in the frequency, made sure the tuner had everything matched and transmitted my callsign with 25W. The meter on the tuner only read approx. 2.5 W (USB).
No signal report.
Then I increased power to 50W and re-transmitted my call. This time, them meter read approx. 4W (USB). So i bumped up the power again to 100W and transmitted my call. The tuner's meter read approx. 7W (USB). When I key down in the CW mode, 100W output reads about 67W (CW). Not too bad, considering I am using an inverted vee cut for a much different frequency.  It is when I transmit on USB that I am wondering if there are any problems.
My question is: Does this seem normal? I am aware that the output is going to fluctuate with increases and decreases in the volume of my voice, but should the power output be THAT decreased? I had the mic gain turned all the way up, also and that helped a little, but I still saw nowhere near the power output that I thought I should have (or that I saw on CW). Does this sound like an equipment issue (due to the mod), operator error, normal operation, or perhaps a matter of getting the settings properly aligned (mic gain and ALC?).
I am using an inverted vee with apex at approx. 30', and each leg cut to about 45' (about 10 MHz).
I was curious because I want to operate with as much power as is required to make contact, and no more, and there is another net tonight that I wanted to participate in. Any thoughts?
Thank you in advance for your advice!

Gerrit
KE5HVM
NNN0XPDT

P.S. I posted this earlier in the Elmers forum, forgetting that the MARS forum was here...Sorry for the double post!
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W3LK
Member

Posts: 5644




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« Reply #1 on: July 10, 2006, 04:51:56 PM »

Gerrit:

This really isn't a MARS-related problem. You are getting some good help in the Elmers forum, which really is the correct place for the question.

Hope you get the problem fixed soon.

Lon - NNN0OOR / NNN0GAW THREE
MDE Navy-Marine Corps MARS
Proudly Serving Those Who Serve
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
K3WVU
Member

Posts: 491




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« Reply #2 on: July 11, 2006, 05:05:39 PM »

Gerritt,

I suspect that your problem is due to RF feedback on the frequency you're using.   I experienced a similar problem in the past with either my 718 or 706MKIIG (can't recall which) on frequencies close to 40M.  I fixed the problem by installing several snap on ferrite beads on the feedline close to the antenna feedpoint.  At the time I was using a MFJ-949E manual tuner.  I purchased the ferrite beads from surplus sales of Nebraska.
The 718 is a good little rig and should give you excellent service on MARS.

Good luck.

Dwight
NNN0TPR
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G4FFD
Member

Posts: 1




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« Reply #3 on: July 18, 2006, 08:36:08 AM »

I had a similar problem with the IC-718.  Check the power supply for correct output, using a dummy load.
My voltage sagged under load due to a failing rectifier.
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KD4TWP
Member

Posts: 28




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« Reply #4 on: August 11, 2009, 04:56:20 PM »

I also had this problem mine started in kuwait and iraq this year i wasnt able to run a ground there and used a mfj artifical ground.,i didnt mess with think about the power thing until i got back home and found when i hooked the rig to a ground the power came back up to 100 watts.but i still added a choak close the the ant connecter just in case.
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