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Author Topic: Preamp question for 756Pro3 owners please.  (Read 1099 times)
KC8CXZ
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Posts: 85




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« on: May 03, 2009, 12:24:00 PM »

Is it normal to have an 'S3' noise level on 6 meters SSB with the Preamp on in 'position 1'?  This new rig seems very noisy on 6m compared to my older rigs, where even with the preamp on, register much lower on the S meter than the Pro3.

What does your Pro3 register on 6m SSB with the Preamp on 'position 1'?  Just curious.

Thank you.

73, Jim
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N6NKN
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Posts: 425




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« Reply #1 on: May 03, 2009, 01:14:05 PM »

Where is the S meter when the preamp is off?? On mine: preamp off S-0, preamp 1 S-0, preamp 2 still S-0.

Rick N6NKN
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W4VR
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« Reply #2 on: May 03, 2009, 01:30:33 PM »

Should be at S-zero even with Preamp #2 turned on.  If you have a rotatable beam on 6 meters you may try rotating it to see if the noise varies in intensity.  If it does, the source could be coming from a power line.  I had a similar problem to what you're experiencing and it turned out to be a bad connection in a 480 KV transmission line within 2000 feet of my house.
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K7PEH
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« Reply #3 on: May 03, 2009, 04:20:07 PM »

First, I will admit that I have never operated on 6-meters but I do have a Pro III.  My antenna, in this case, is my Traffie 5-band hexbeam.

So, I am curious, is there something special about the 6-meter band that the noise level should be zero (with any preamp setting: off, 1, 2)?  My noise level is 0 (roughly) with no preamp, about S1 with preamp 1, and S3 (or a bit under) with preamp 2.

So, is 6-meters supposed to be noise free?
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KC8CXZ
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« Reply #4 on: May 03, 2009, 05:58:14 PM »

Interesting responses.  With no antenna connected on the Pro3, I get 'S0' with no preamp as well as preamp 1 and 2 switched in (on 6m SSB- CW is much lower).  With my 'KU4AB square' loop, I get the previous readings I mentioned in my original post.  The HF bands are rather noisy as well, but I can't tell if all this interference is just QRN (atmospheric) or if it is power line interference.  I guess I need to find a good website and/or book on solving this.  If the radio is defective, I need to send it back before the warranty runs out.
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VE7REN
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« Reply #5 on: May 03, 2009, 06:30:03 PM »

the band has been very noisy lately....i mean staticy,qrn,etc...,with all 4 of my radios showing s3-7 all the time. i would say nothing is wrong with the radio, just bad conditions,or.... for your own sake, try the radio on a friends or other  6 meter antenna to take all doubts away??the pro 3 is one hell of a rig!!
ve7ren brent
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WA3SKN
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« Reply #6 on: May 04, 2009, 04:57:48 AM »

With the antenna jack shorted, any noise heard will be internal to the receiver. So you should have no meter reading... that would indicate an AGC voltage feeding back to the RF/IF stages.
Connect the antenna. Whatever noise increase is incoming from the antenna. Since atmospheric noise is minimum on 6 meters, I would suspect a local noise source in the area of your antenna to be the problem!
Are there any LANs in your area? A 100 Mbit LAN is a 50 Mhz square wave... rich in harmonics and noise, and ever popular at this time! Those CAT5 wires are nothing more than an antenna radiating the noise locally!
Time to find the noise source and shield or filter it!
Good luck with the project!

-Mike.
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W8KQE
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« Reply #7 on: May 05, 2009, 10:42:44 AM »

I have the same issue!  My FT-450AT, with the preamp on, and using the SAME 6m loop antenna as my Pro3, shows NOTHING 'S-0' on the 'S meter' when listening to a dead band on 6m USB.  When I try my Pro3 on that same antenna, the S-meter reading is S-0 without the preamp... S-3 with 'preamp 1', and almost S-5 with 'preamp 2'!!!  Of course, most Hams do 6m weak signal work with at least the preamp in 'position 1' with their Pro3's.

Thus, the Pro3 sounds MUCH noisier and fatiguing than the FT-450AT!  The 'grass' on the bandscope is 2 squares tall with 'preamp 1' on.  I'm wondering if this is a normal characteristic for the Pro3, or if I got one with a bad DSP unit.  Anyone else experiencing high QRN levels these days?
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N4UE
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« Reply #8 on: May 05, 2009, 03:07:34 PM »

Jim, (an the group), I don't have a PRO III, but I do have the original PRO I hand carried back from Tokyo, just after they were announced.

I live in a VERY small town, here in North Florida. I am the last person on my power distribution AC line. However, I have fought powerline noise since 2003 when I moved in. At first, just a random long wire would produce S-7+ on my old Collins 75A-4.

As I got more antennas in the air, (and unpacked more radios) it became VERY obvious, I had some serious (!!) powerline noise.

I made a couple of Kent Britton's 'cheap yagis', and started walking the neighborhood with a little Icom R10 receiver. The 9 element 435 MHz yagi was VERY sharp and identified several offending poles.
An e-mail to Florida Power and Light got an immediate response. They sent out a really nice guy, an RFI 'troubleshooter' and he had some pretty nice gear. He confirmed my findings, and put in a work order, to tighten connectors and replace lightning arresters.
To make a long story short, it took mutiple tries, BUT, now it's dead quiet here.

Here's a perfect scenario......
Antenna #1..."fan" antenna for 20M through 10M.

I turn on the PRO and listen to 20M. Sounds fine, no preamp, very low background noise
As I go higher in frequency, I see the noise peak on some bands. 17M seemed to be rather noisy, or maybe the antenna works better there. Turning on the preamps would produce a series of noise spikes, like a comb with the teeth facing up. It would usually get worse the higher in frequency you went. 40M and 80M? DEAD quiet, using the fan (not efficient, but I also have several loooong wires, everything goes through a tuner).

Antenna #2...a simple 6 m dipole at the same height as the fan, 50' or so, They are connected end to end, so they face the same direction. Fed with seperate runs of RG6Q.

If there is 'noise' nearby, you will hear it on the dipole! Just yesterday, I was listening on 6 M as the band was trying to open. Preamp 2 on, noise level just perceptable when the antenna is connected.
Heck, I can see the horizontal oscillators of several nearby TVs down around 50.113... No matter where I have lived, I always hear these artifacts.

These findings are not just with the PRO. I have a bunch of 6 M radios including a mint Drake TR-6, about 10 6 M converters and a huge collection of receivers.
I have yet to find any combination of the above equipment that can do better than the PRO for weak signal / scatter.
Maybe 'cause it's the 'European' model? Maybe 'cause I hand carried it? ha ha? DUNNO, IT JUST WORKS.


May I offer a suggestion? The ARRL has a fantastic book dealing with RFI / Power Line Noise.
A lot of the things in the book were not published years ago when I first became a target of this dreaded noise.

You will leark a LOT about 'loose hardware'!!!! ha ha

73

ron
N4UE
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KC8CXZ
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Posts: 85




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« Reply #9 on: May 08, 2009, 05:16:05 AM »

Thanks for the replies and info!  

I'm not convinced that the noise level i'm receiving on the Pro3 is man-made.  I know W8KQE from local Hamfests, so I called him up after reading his post here, and he brought his FT-450 over to compare with my Pro3.  Sure enough... with the preamp on (6m SSB- band 'dead') the FT-450, there is no S-meter deflection, and the noise floor sounds nice and quiet.  Using the same 6m loop antenna, on the Pro3 with 'preamp 1' on, I get S-2 to S-3 of what appears to be QRN, and 2 square grids high on the bandscope.  With the preamp off, the noise floor sounds 'normal' and quiet.  Could it be that the preamp is defective on the Pro3?  
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K5DVW
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« Reply #10 on: May 08, 2009, 05:22:57 AM »

You could be overloading your receiver. Do you have a local Channel 2 TV station? That's a few MHz away and could be smacking your preamp pretty hard. You didnt say if it's broadband noise or not.
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K7PEH
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« Reply #11 on: May 08, 2009, 09:09:15 AM »

Why are you not asking the more obvious question?  That is, assume that the noise is indeed there and real no matter what it's source is.  Then, ask why your other rigs do not "hear" the same levels of noise.  Could it be that they are not as sensitive?
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KB4QAA
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Posts: 3268




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« Reply #12 on: May 08, 2009, 11:21:33 AM »

hmmm

- You've already proven the noise is not coming from your radio by disconnecting the coax.

- If you use a pre-amp you shouldn't be surprised when the noise level on any given frequency goes up. That's what they do, amplify everything.

- If you don't like what you are recieving with preamp on, turn it off.  No filter/preamp/modifier is appropriate for all band band conditions. (and just to sound like the old fart I'm becoming, we didn't have them at all just a few years ago).

- Sweep the band and see if there is a pattern to the noise.

- Build a Yagi or Moxon and see if there is a directionality.

- Take your rig and Yagi mobile and do some df'ing.

- You may just have to accept that there is some sort of man made interference in your area.  You may find that it varies with weather condition, season or workday.  Smiley

Good luck guy!  Bill  
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KC8CXZ
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Posts: 85




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« Reply #13 on: May 10, 2009, 05:22:07 AM »

UPDATE!

Well this is GOOD NEWS!  I turn the Pro3 on this morning, and even with the preamp in 'position 1', the band/noise level was quieter (6 meters)!  My S-meter is now registering only about 'S1'.  Which must mean one thing only (bear with me... i'm learning!).  Mainly, the excess 'noise' I was receiving and concerned about these past few days was nothing but atmospheric noise/QRN!!!

Has anyone else noticed noisier bands lately???!!!

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N3OX
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« Reply #14 on: May 10, 2009, 08:54:58 AM »

"Mainly, the excess 'noise' I was receiving and concerned about these past few days was nothing but atmospheric noise/QRN!!!
"

Or local manmade noise that is intermittent...

I've got a few noise sources around here that are mercifully seasonal.  Something horrible comes up on 160m once the weather gets warm, and goes away for good by October.  I think it's air-conditioning related.

Others can be quite random.  Someone unplugs their cordless drill's battery charger for a while to plug in the belt sander, or someone gets rid of a noisy TV.

Power line noise is often intermittent and weather related, but usually you can tell that by the buzz, especially if you put your rig in AM mode.

There's not a lot of atmospheric QRN on 6m because it's closed much of the time these days.  My entire noise floor is manmade.  If I shut off my noise blanker I have S7 power line noise in some directions.  Fortunately, the noise blanker gets rid of that, but there's still a significant noise floor above the radio's basic noise, and most of it sounds manmade.



73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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