Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 3 Next   Go Down
  Print  
Author Topic: Noise Levels on 75M  (Read 1510 times)
KN4LXH
Member

Posts: 12




Ignore
« on: November 01, 2018, 07:34:06 PM »

Don't work much on 75M. Every time I tune in to the 3902 KHz or 3905 KHZ I get an S9 noise level. If I tune to the top of the band the noise level drops to S7. I work mainly 40 and 20M. If you work 75M a lot, is this typical for that band?

My equipment: Yaesu FT-991A Transceiver
                     LDG AT-1000 Pro II tuner
                     Samlex 15V switching power supply
                     Alpha Delta 40-80M Inverted V (strung in a tall pine tree)

Thanks
Jimmy
Logged
WZ7U
Member

Posts: 1073




Ignore
« Reply #1 on: November 01, 2018, 10:44:12 PM »

How about turning the attenuation on? That will drop the garbage down so you will have an easier time picking out who you want to hear. Try that and get back to us, because what you are describing is typical of that band as well as anything below about 10mhz. While everything you hear will be quieter, you can make up for it by riding the volume knob.
Logged
KC8KTN
Member

Posts: 1870


WWW

Ignore
« Reply #2 on: November 01, 2018, 11:31:31 PM »

I recommend an Icom 7300. The BEST.  It is a world of difference from a Icom 718..
Everyone have a Joyous Day.. Be Safe 73s

Jesus keep me focussed . Give me Patience... 
Logged
K1FBI
Member

Posts: 202




Ignore
« Reply #3 on: November 01, 2018, 11:55:16 PM »

I recommend a Hilberling PT-8000A, it to is a world of difference from an Icom IC-7300.
Logged
K1FBI
Member

Posts: 202




Ignore
« Reply #4 on: November 01, 2018, 11:55:58 PM »

Now back to the original question. 75m is a noisy band. Especially during the day and summer months. The attenuator as mentioned and turning down the RF gain while turning up the volume works well. Also unless you are going for DX, this is the time where a lower antenna will actually serve you better
Logged
KB2CRK
Member

Posts: 154


WWW

Ignore
« Reply #5 on: November 02, 2018, 06:09:32 AM »

Don't work much on 75M. Every time I tune in to the 3902 KHz or 3905 KHZ I get an S9 noise level. If I tune to the top of the band the noise level drops to S7. I work mainly 40 and 20M. If you work 75M a lot, is this typical for that band?

My equipment: Yaesu FT-991A Transceiver
                     LDG AT-1000 Pro II tuner
                     Samlex 15V switching power supply
                     Alpha Delta 40-80M Inverted V (strung in a tall pine tree)

Thanks
Jimmy


I had an issue very similar to that. Turns out one of my laptops in the shack had a bad power cord. When it was unplugged all of the noise went away.
Logged

some people are like slinky's. not really good for anything but still bring a smile to your face when you push them down a flight of stairs.
W9IQ
Member

Posts: 3075




Ignore
« Reply #6 on: November 02, 2018, 06:19:07 AM »

The addition of a proper current balun at the feed point of the inverted V may also help. Without it, the coax will tend to pick up locally generated noise and couple it into the receiver.

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
VE3PP
Member

Posts: 164


WWW

Ignore
« Reply #7 on: November 02, 2018, 07:48:12 AM »

I recommend an Icom 7300. The BEST.  It is a world of difference from a Icom 718..
Everyone have a Joyous Day.. Be Safe 73s

Jesus keep me focussed . Give me Patience... 

Please enlighten us how an Icom 7300 will combat locally generated noise?

The original poster is not using an Icom 718, which claim is inferior to the 7300.

Your post makes absolutely no sense.

God needs to give us patience to deal with you.  Roll Eyes

To the original poster, make sure your pre amp is not turned on. I normally see S 5 (currently at 14:43 UTC.)

At night, depending on conditions that noise level could rise up to S 7-9.

Antenna is a fan dipole for 80/40. Radio is a FTDX-1200, but I have 4 additional HF stations here and the noise level will be the same on those too.

I know that on my FTDX-1200 and FT-950 the factory default for the pre-amp is Amp 1. So make sure you have that turned off.
Logged
KC0OW
Member

Posts: 9




Ignore
« Reply #8 on: November 02, 2018, 07:57:13 AM »

jimmy,

greetings!

couple of things, if ur swr is flat around 3905 and exceptionally high at the upper end of the band u may have hit the sweet spot around 3905 and everything will be a little stronger.....signals and noise floor.  the other thing that may be going on is that u may be picking-up some local noise around 3905 and the only cure for that might be to get that wire up even higher than it is now.  i've found that height is might when it comes to getting rid of local noise.

also, if you've got about 180-200 feet available, u can try a B.O.G. receiving antenna(s).  see the fellow at LBS who can set u up with one or more, of those.  they're sure to make ur 75/80m radioing more enjoyable.

regards es best 73's de kc0ow, scott.
Logged
K1FBI
Member

Posts: 202




Ignore
« Reply #9 on: November 02, 2018, 08:13:13 AM »

Strange, I've found just the opposite to be true.
Logged
KN4LXH
Member

Posts: 12




Ignore
« Reply #10 on: November 02, 2018, 09:11:48 AM »

Somebody mentioned turning down the rf gain( I think). So I looked at the screen of the 991A and the amp1 icon was on. I reset the IPO function to bypass both preamps (AMP1 and AMP2) and the noise level dropped from S9 to S6. Thanks!
Radios are so complex nowadays that I may have risen to my level of incompetence already.

Bye the bye...somebody mentioned noise sources. Does anybody sell a device that can pinpoint sources of RF noise
or maybe somebody has a schematic for a simple device.

Thanks
Jimmy
Logged
WZ7U
Member

Posts: 1073




Ignore
« Reply #11 on: November 02, 2018, 09:17:20 AM »

I recommend an Icom 7300. The BEST.  It is a world of difference from a Icom 718..
Everyone have a Joyous Day.. Be Safe 73s

Jesus keep me focussed . Give me Patience... 

Please enlighten us how an Icom 7300 will combat locally generated noise?

The original poster is not using an Icom 718, which claim is inferior to the 7300.

Your post makes absolutely no sense.

God needs to give us patience to deal with you.  Roll Eyes

To the original poster, make sure your pre amp is not turned on. I normally see S 5 (currently at 14:43 UTC.)

At night, depending on conditions that noise level could rise up to S 7-9.

Antenna is a fan dipole for 80/40. Radio is a FTDX-1200, but I have 4 additional HF stations here and the noise level will be the same on those too.

I know that on my FTDX-1200 and FT-950 the factory default for the pre-amp is Amp 1. So make sure you have that turned off.

Ah, I see you've stepped in some of our village idiots excrement. I hope you were wearing shoes. Our apologies, sometimes the scooper patrol misses things around here.

Its best to simply ignore his baitings or you will be lumped into his fictional Wound Too Tight Club. In which case you will be ridiculed at every opportunity. If you spend a little time looking up his previous postings here, you will see the ravings of a lunatic self evident in short order.

If you have the appropriate software enabled, this video will explain everything perfectly. I find that the phone has no trouble playing the file.
http://photobucket.com/gallery/http://s926.photobucket.com/user/Bob_Bralove/media/KC8KTN%20The%20CB%20Captain/KC8KTNTheCaptainVideo2.flv.html

Logged
KD3WB
Member

Posts: 148




Ignore
« Reply #12 on: November 02, 2018, 09:26:45 AM »

If you have a twelve volt car battery, use it to power the rig, then turn off all the electricity in the house.  If the noise decreases or disappears, turn each breaker on one at a time until it returns, then find out what is using that part of the circuit.

Ben
Logged
KM1H
Member

Posts: 4802




Ignore
« Reply #13 on: November 02, 2018, 10:09:34 AM »

Once the feedline is decoupled then it is time to tackle all the in house noise sources and these days they are  many.
I use a battery BCB portable to go thru every room and then apply ferrite or foil shielding as needed. The final test is to shut off the mains breaker......and then having to reset all the devices that have a clock feature.

Isolating sections of a home works for many but that is too much walking to the basement for me due to the size and layout of my house.

I also use whole house MOV's right at the panel to further reduce incoming noise and have even built LPF's into outlet boxes and strips.

The result of all this work, and some not insignificant expense, is a fairly uniform amount of atmospheric noise only per band that does allow me to hear quite well.

The SNR can be improved on any mode by narrowing the IF bandwidths by the stock or optional filters plus the rigs own passband controls. The worst SNR will be on AM, then SSB, and down thru CW to FT8 and other digital modes. CW use appears to be increasing during these times of poor propagation based upon my regular listening.

Carl
Logged
KC9NVP
Member

Posts: 297




Ignore
« Reply #14 on: November 02, 2018, 10:30:31 AM »

Jimmy, you asked: "Does anybody sell a device that can pinpoint sources of RF noise or maybe somebody has a schematic for a simple device." 

The answer is yes.  First you may want to review some of the comments and discussions in the RFI discussion group on this web site. A spectrum analyzer with the proper frequency range and directional antenna can be used to get a bearing on which direction the noise is coming from, or as indicated in the RFI discussion group, a small short wave receiver radio will work as well. 

As Ben (KD3WB) indicated, if possible run your radio off of a car battery and kill the power to your house to see if the noise goes away, if so something in your house is causing the issue, if not then you need to search outside your house for the source.

With regards to spectrum analyzer, there are several hand held units on the market so do a web search and you should find information.

David
Logged
Pages: [1] 2 3 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!