I have a dilemma.....I'm in a place where an external outside antenna isn't an option. For years I've managed with a home brewed center-fed dipole in my attic. Have made hundreds of DX QSOs and have been generally happy. With the band conditions seeming worse now (as compared with a few years ago) I've been noticing that I may not be hearing as much as I ought to. I know other folks can hear me because when I am calling CQ I can see folks lighting up on my QRZ page map....but I don't hear their calls. Other times I've had a few stations calling me as a relay for someone who said they heard me 59+10 yet I couldn't hear them at all. Bottom line, I'm getting out with good audio and a strong signal, but I don't always hear the other side.

I'm running an old icom 718 and using a clearspeaker DSP.
I've gotten pretty good with cleaning up band noise between the receiver adjustments and the clearspeaker, but obviously I'm missing a lot of opportunities.

Part of me thinks this is a a simple matter of getting a proper, well positioned antenna outdoors.
Yet, if the antenna was truly the issue, shouldn't that work both directions? On multiple occasions I get great RST reports yet I am struggling to pull in the DX station. If this was purely an antenna issue, I'd think they wouldn't be hearing me either?

The other part of me is thinking that it's time for a modern, more sophisticated receiving end....perhaps something like a new icom 7300.
I hear from owners that the onboard filtering is night/day compared with the older gear and that you can pull even the weakest signals out. Of course, I'm concerned that I'll drop the coin for the new toy and my limited antenna will render the modern hi-tech receiver to the same marginal window of reception.

Would love to get some thoughts and feedback from you guys.
I'm working on getting my rig outside in the very near future....just waiting on a few parts, then plan to drive to the top of a big hill, set up a dipole about 25ft up, and see how the overall performance is. Still, I find myself wondering what a modern rig could do better than my old workhorse horse 718.

Thoughts?

Have you checked transmission line losses and antenna matching?

Try a common mode choke before changing anything else, if it's a matter of signal to noise ratio in your receiver.

That seems sort of backwards, to my situation.

I also run attic antennas (100 watts max), and the TX/RX capabilities seem about equal.  Unfortunately, often times, I don't hear DX stations that everyone else can hear.  For instance, I might see someone on the  spotting nets say that a particular DX station is strong here in Dallas.  Or everyone  here on Arfcom is having good luck working one of the rare DX stations.  But I don't hear anything.  On the other hand, if I can hear them I can work them.  

I'm running a K2 and a K3, so I do have good receivers. But my antennas are only about 15 feet above the ground, and all of the electrical and mechanicals are in the attic too, since my house is built on a slab.  

Not sure what is going on with your problem, but I hope you get it figured out.  Good luck with it!

What about trying digital modes?

This makes sense to me.

Strongly consider the 7300, you will be amazed at what you are missing.  The spectrum scope lets you see what signals are out there and the filtering is night and day over the 718.  Much easier to operate in digital modes.

Running an auto tuner and typically match SWR to 1.5:1 on average.
In the process of redesigning a few elements to improve that and get closer to 1:1

I do know that the coax running to the balun could be better...will be swapping that out with some RG213U soon....just been too lazy to go up and swap the cables

Thing is, I do phone for now...might break into other modes when time permits but for the time being, I'm working phone.
7300 is a big ticket item but if its going to dramatically improve my receiving capability I might be into it.

It will over the 718.  Ever since I bought my 7300 I've done a ton more phone since I can see the signals, tap the screen twice and I'm there.  No more spinning the knob and hoping I find someone when they are talking.

Funny, my ANAN is the same. :P

Like said above -------- Signal to Noise Ratio.

If you're being heard, but not hearing, then the only relevant factoid is that your antenna is picking up too much noise and is covering up a roughly equally strong signal (on the average) from those trying to call you..

As mentioned, a common mode choke can help.  Naturally, you want to make sure your antenna connections are intact.  Re-location and re-orientation can also help.  Following all the standard techinques to isolate noise sources in your house is also a good idea.

You can try this, but using an attic-mounted antenna you are almost certainly picking up a lot of noise from in-home electronics. Another good possibility is local power line noise.

The only thing you can really do is move the antenna further away from the noise sources, or reduce the noise.  Power line noise usually has a recognizable buzzing at the line frequency, but not always.

You could make a concerted effort to unplug all the electronics and anything else with a wall wart or other power supply, as well as making sure all fluorescent and LED lights are off, and see if that makes a difference.

What is your noise level?

I was in a townhouse and had the same problem, because the line noise was terrible. This was in the early '80s before the invasion of all the consumer electronics devices. Back then, everything, including my old Radio Shack computer, had analog power supplies. A good DSP noise filter will knock a lot of the noise down to manageable levels.

What value of torrid core do you guys recommend for the antenna feed line?
How about the power supply leads going to the radio?

For the low cost of a couple of cores and some wire it's an easy enough thing to play with.
I can easily wrap one for the power supply leads....will need to build something for the antenna coax.
I ran the thinker line early today....decided to stop being lazy and upgrade the line. No major impact, at least not that I could tell with the few minutes I had to test it.

On another tack.....I've always struggled to get below a 1.5:1 SWR.....suggesting the antenna elements aren't perfectly resonant. This hasn't seemed to hurt my transmissions at all...but could that be having an impact on my ability to receive.

To put things in perspective, I rarely have any trouble getting through a pileup to a DX station during a contest...and this is running barefoot. For years I never really thought about all the calls I was missing coming back from the other end. Does this seem more like a matter of SN ratio...or...is it plausible that having the antenna under a shingled wooden roof is filtering off and attenuating the inbound signals? I'm guessing it's some combination of the two but I'm trying to figure out which is the larger contributor, so I can attack the largest variable first.

Just out of curiosity, are you using a balun at the feed point of your antenna?

This is a great read:


http://audiosystemsgroup.com/RFI-Ham.pdf


It has a lot of suggestions for toroid cores, # of turns, etc backed up with measured data.


I built a common mode choke using data from this article and it reduced receiver noise by 3 S-units when using a portable vertical antenna indoors.

So I think I have this nailed down to using a FT240-43.....but the design I see being popular calls for 8 of them...and they seem to be around $10 each. This just keeps getting more expensive.

Anyone know a low cost place to get torroid cores?
(Or a choke design that would be effective using less cores?)

Don't underestimate the quality of the radio when starting in the hobby (2007). I had delusions of tacticalness and initially bought a FT-817. That was a train wreck. Then I bought an IC-7000. All I ever did was run digital. Then I bought a used Flex 3000. Oh. My. God. It was like I had crawled out of some dark place and into the light. I could hear things, and sounded good, too. I started to run mostly phone. Now I have an ANAN-100D.

These days I would have a very hard time recommending anything less than an IC-7300 for anyone starting out. Yes, it seems expensive, but how much is the dust that gathers on top of the radio that is never used worth?

Well...I found torroid cores for about $5 each, so I'll give this a shot and see how things play out.

Would it make more sense to place the choke on the line between the tuner and the radio (last possible section of wire before going into the rig)....or....should the choke be between the antenna and the tuner (the end of the feedline right before going into the tuner)?

I would think it should be as close to the radio as possible, but I've seen some folks saying it should be outside the shack entirely.

For reference, the shack is directly under the attic...I have a 1:1 balun up at the peak of the roof (maybe 15'-20' up from the radio, through a sheetrock ceiling, and probably 25'-30' up in a straight line away from the radio. From the balun to the tuner (LDG IT-100) I'm running 50' of RG213...from the tuner into the radio there is a 1' connection cable that came with the tuner...not sure what type of wire it is...no markings.

So where would be the best place to put the balun on the feedline for noise suppression?  Feedpoint, where the feedline enters the house, or at the rig?



I'm following this closely because I have wicked hash noise on the low bands.  I chocked it up to being in the 'burbs, but I've got some large Mix#31 toroids that I bought for this purpose but never really used.  I'd like to see if I could get the noise on 40M down a little bit with a choke balun of feedline wrapped a few times through a few of these.



I'm running an OCFD above the house but fairly low to the roof, with a Balun Designs 6:1 current balun at the feedpoint.



Thanks!

The choke needs to be at the antenna feedpoint. What it's doing is blocking noise that is picked up on the coax shield (while simultaneously pushing signal into the coax vs allowing the RF to flow on the outside). It doesn't hurt and may help some to put one at the radio end also, but the main benefit is at the feedpoint.

Thanks.  The balun I'm using on my OCFD is a Balun Designs 4115 that is touted as having excellent isolation and choking impedance.  I figured that at the feedpoint would be enough.  Boy was I wrong.





I just decided "screw it" and went up into the attic where the coax enters the house and made a choke of 6 turns of my RG-8X feedline through 3 large mix 41 torroids I had.  Then I did the same right before the radio.





HOLY CRAP!





Noise on 40M went down from S8-9+ right before I did it down to a solid S5 without DSP enabled!





Now I'm pissed that I hadn't done this earlier





 

Nice....and encouraging. I ordered cores today....hope to have a similar experience in about a week or two.
Also pulled apart my rack and removed all extraneous items that use AC power....tried to clean up the cabling a bit.
Going to do everything I can to improve the antenna system before buying a new radio. I figure this setup gives me a nice test bed to see just how good I can get the antenna system....if I choose to add a really nice radio with good filters at some point later I would think things would be that much better for pulling in those weak DX stations.

Foe what it's worth, I had a 59+20 report from about 500 miles out a couple hours ago after I cleaned up the cabling.
The TX side of things is doing its bit....and I pulled in California from 3-land with no problem mid morning on 20m.

Really looking forward to seeing what I can hear after the choke is wound in place.


Thanks to all for the advice and guidance.

I had a similar epiphany a couple years ago. It's amazing how much noise long runs of coax produce, or even short runs.

I used to think that toroids were just a dirty fix for a problem that could otherwise be solved by good grounding and good coax. Boy was I wrong. I keep a couple 41 mix 240 size toroids around now, and have about ten of them in-service.

To add another facet to the discussion, don't overlook the antenna design itself.   A high Q antenna such as a screwdriver will pick up less noise for a number of reasons including it's tight bandwidth, and you really don't take much of hit on gain at 40M and above.   It might be practical if the attic space is tall enough.   It also eliminates the radiation angle penalty that comes with a dipole at less than optimum height, and at the same time flattens out the sphere from which you are presently picking up noise (though that sword has a double edge, and may pick up more noise from the neighbors BUT see the narrow bandwidth argument again).

Of course you have to throw down several hundred bucks for a good one along with a proper controller, and then custom fab a mount and radial system.    

Since they are usually associated associated with mobile use, they are often overlooked as the great limited space fixed station antenna they can be.

UPDATE....and no luck

I got 10 torroid cores in the mail today.
Turned on the radio as it was configured and tuned to 14.5MHz....was seeing a noise floor on my meter of S7.5
Disconnected the antenna cable.....S meter dropped to 0 and all noise was completely gone....so at least I know the noise is coming from the coax.

I wound the end of the RG213 five times through the 10 cores and plugged the antenna wire back in to the radio....still at the exact same S7.5

Now I know that the recommendation is to place the choke at the feedpoint....and I will still try that when I get a chance....but unless I'm missing something, wouldn't placing the choke at the last point along the path actually work better if not at least provide some impact?

Should I be taking a non-coax lead between the wire antenna and the balun and wrapping that in the cores?
I think I am also going to eliminate the balun for testing purposes to see if that could somehow be introducing noise.
Really bummed....dropped $50+ on these cores and so far its a bust....did nothing to reduce noise.

Am I missing something?

I think you're missing how ferrites work. Putting them at the radio does about as close to nothing as possible, for this kind of noise anyway. They can't affect the signal on the inside of the coax. If you had a significant RF-in-the-shack problem that might be helpful.

What you are trying to stop is the noise that is on the outside of the coax and flowing UP the coax. Noise picked up on the outside of the shield flows up to the feedpoint, then mixes with the antenna signal and goes down the inside of the coax. Ferrites create a high impedance path to block the flow of RF. At the feedpoint, that means that signal RF on the antenna gets forced into the inside of the coax instead of going down the outside. Simultaneously, they block noise RF flowing up the outside of the coax from getting into the inside.

The biggest problem that you have with your attic installation is that the antenna is also very close to the noise sources; blocking the flow of noise from the coax shield won't help when the noise is being directly received by the antenna itself.

Thanks for this....another question...

Up in the attic, the coax runs to a balun, then the two leads coming from the balun touch the two sides of the dipole. Is there value to placing the choke between the balun and the actual antenna elements, or does it need to be on the coax right before it connects to the balun?

So I got up there this morning and did some testing....

Turned on the radio and tuned it again....noise level was S7.5...



I went up to the attic and disconnected the coax from the balun.....checked the radio again and the noise was totally gone and the meter was at S0 (as I expected, but wanted to rule out the physical coax cable itself.

Took the balun totally out of the mix and wired the coax directly to the dipole....back to S7.5

Then wired up the choke using 10 cores with 4-5 turns inside of it....



Absolutely no difference is noise
For a goof I disconnected the attic fan....that made no difference either.

So now I'm back to square one...I have ruled out the cable, the balun, the attic fan, tried the choke on both ends, upgraded from RG8x to RG213....I'm at a loss.

I'm thinking of setting up the rig on a battery and then killing the main panel breaker to the house....completely take the entire house off the grid and see what kind of noise I get then....it'll be a while before I can run that test.

Also looking at notch filters...seem to be a few MFJ models that could help for audio frequencies....but what I really want to do is get the SN ratio down from where it is today. I'd much rather clean up the signal rather than spend money to clean up the output to the speaker.

Any thoughts or advice at this point?
Is the RG213 maybe too thick for this application?
Its a 50' run between the feedpoint and the rig. Would the choke work better on he RG8x? (I upgraded because the RG213 was listed as having a lower loss over the same distance)

It sounds like the antenna elements themselves are picking up the bulk of the noise.




Putting ferrite chokes on the antenna elements would be counterproductive, to put it mildly.




Another thing to try is perhaps a magnetic loop antenna. Very high Q so good noise rejection. The compromise is having to re tune for practically every frequency change. You would want a remotely tuned one so you could mount in the attic. MFJ makes several but they are expensive. If you do a lot of digital work on a single favorite frequency, a manual loop tuner in the attic would be a decent choice.


 

Another member mentioned screwdriver antennas. That's another good suggestion if you have the height inside the attic.


But if you have done your best to improve noise rejection, then logically you are left with noise reduction (finding and eliminating noise sources in and around your home) and as a last resort, finding a way to get an antenna outdoors without conflicting with whatever prevents you from doing so...

I did a little more testing since the last post...in the shack I fashioned a little antenna with some wire elements hanging off a 1:1 balun and run that into the radio with a 1' coax cable. As expected, noise was minimized to almost nothing. Will try to move that test antenna up to the attic and verify the same experience over the 50' run, but I am pretty certain I'll get the same result. As you allude to, this suggests that maybe it's time to rethink the antenna. At present I have wire running all over the attic.....perhaps there is just too much antenna and I'm simply getting every bit of noise through it.

Will be experimenting with some other dipole designs and see if something else yields a better SN ratio.
Time to rethink my antenna.

Before you drive yourself too crazy, do a few simple tests.



First do the "breaker test" where you hook the radio to run off a battery and shut off the main breaker to the house.  If the noise is coming from inside the house, that is good news because you are in control and can deal with the offender.  I had one noise source I couldn't find that was driving me CRAZY, turned out to be the power supply for my ADS-B receiver.  Was hooked up in the attic, so I never remembered to unplug it during my usual 'rounds'.  Replaced the switching supply with a linear and all was good.



Also, switch the radio to AM and listen to the noise.  Better yet, if you can, make a recording and post it for us to hear.  If you hear a 120HZ bacon sizzling sound, it is probably power line noise from outside the house.  Here's a recording made by yours truly https://clyp.it/ytcqbtos



Best of luck in your endeavor, I'm constantly battling this problem myself.

The ferrite chokes are good for supressing returned RF back into the shack.  Originally I had a 100 foot run of 240 to my antenna which was much longer than I needed.  I replaced it with a 50 foot run of 400UF but I lost the air choke I had incorporated with all the slack of the 100 foot run.  With the 50 run I was getting RF back in the shack so bad it would buzz the computer speakers on the desk with the radio, and on 40M digital modes I couldn't type and xmit at the same time.  Ordered up some ferrite chokes and clamped 7 of them at the far end of the coax and no more RF back in the shack.  I also clamped the remaining 3 on the coax near the radio (feed line runs past some 110 wiring but I try to keep the intersections perpendicular), but I don't think they do much of anything for me.

Shut off all power to the house at the breakers and run the radio on battery.  As you start to throw circuits back on you can get an idea of where much of your RF noise is coming from.  I had two really bad sources of noise, one was from the TVs DVR system that used a wifi link to the remote set top boxes, and the other was from an inkjet printer when I plugged in the USB cable.

Also, battery chargers, specifically your 12V/automotive kind, will generate a lot of RF noise.  Your shorty test antenna may seem fine as it simply doesn't have the same amount of copper in the air grabbing signals.  On field day I set up my first 160M dipole.  I tell you what, with 80M of copper hanging in trees I had ears like never before.  While it may not have worked as well as I wanted on 160 (height above ground the hindrance), it made for an excellent receiving antenna.

If you have those touch tap sensors for a lamp or other device, those create a lot of local RF noise as well.  Wall warts can be bad too.  Again, cutting power and bringing each circuit online individually will help you isolate noise sources.

Got the new dipole up this afternoon...modified the choke based on some research....noise was down to S7 but in truth, not really anything audibly perceptible....noise is basically unchanged.....except that on 10m and 80m.....there was basically zero noise. I assume 10m wasn't open....but I heard plenty of traffic on 80m and with very little noise. On 40m the noise was closer to S9.....really loud. I'll make an audio record of it and post it when I get a chance.

Weird thing...the 20m element isn't tuning well...can't get much below a 2.0 SWR....I tried to tune moving up the dial and down the dial from the frequency I build the elements based on (14.250) but at no point did the SWR go down below 2. After enough of a stretch up and down the dial it began to drift up to 3.  Keep in mind I'm using the SWR meter on the display on the radio (icom 718) and not convinced of its accuracy.  Interestingly, I heard a guy calling from Gaudelupe with a real nice signal and I through my call out. Had had me at 5x9 +15

Granted the RG213 might have improved signal to the feed point a pinch over the RG8x I had been running, but for that particular QSO my SWR was coming in at 2.25:1 and yet we had a clear QSO....as easy to copy in both directions as a 2m repeater down the street.

Besides the element length....and ruling out other components like the balun and choke for now....what other factors might be creating the high SWR? I'd like to trim the elements if needed.....or add to them if that is the case...but is it possible that other parameters are creating the high SWR? For reference, I can tune all the other bands to about 1.5:1.

To this end, what would be a good manual tuner that has an accurate SWR meter on it? The auto tuner I'm running that integrates with the 718 has served me well....but not having any control isn't helping me diagnose this issue, and I'd like to get a better SWR display in the process.

All I see on the net are primarily MFJ units which seem to always come with mixed reviews.
Any recommendations that won't kill my budget?

Yeah, that isn't accurate at all.

What you should do is get an hf antenna analyzer. They're $130 on amazon and eBay, I wish I had bought one sooner than I did.

I've debated getting an analyzer for years....probably should just bite the bullet and get one.
One one hand I know that if I can figure out the sweet spots on each element I can then trim it or extend it to the best length.

I've seen the MFJ 213 for around $190.....but again I always see mixed reviews about MFJ.
Also see a lot of other very expensive options that are way out of the budget.
Any recommendations on cost effective yet good, functional analyzes?

Well one expensive option you don't need to worry about are the High-Q antennas like screwdriver and small loop (unless you really want one!).

There seems to be a misunderstanding regarding noise pickup.  Noise is a signal just like any other signal, and the antenna bandwidth or Q makes zero difference to the received SNR (as long as the BW of the antenna is wider than the IF bandwidth - which is always the case for ham antennas).

IOW, 2 antennas in the same location, with the same radiation pattern, one with a narrow bandwidth and the other with wide open bandwidth produce EXACTLY the same SNR on the received signal.  ALL other wideband noise is filtered out by the radio's IF filters - that's what they're for!!!

However, note that one advantage for a small loop is to utilize the nulls by pointing it / them at the worst of the noise sources if possible.  Of course this works because of the directivity of the loop, and has nothing to do with it's bandwidth.

I've got the RigExpert AA-30 and really like it.  Its only $224 w/ free shipping from Gigaparts.

I've heard too much bad stuff to buy expensive electronics from MFJ.

HF Noise

Above is a link that may help better explain noise and how to see what is causing the problem.

Don't get discouraged and good luck in tracking down the problem.

Thanks for this...its been an interesting week.
Talked to a lot of guys on the local 2m repeaters. Got a lot of feedback, advice, and perspective from folks in my area.
I've made progress with setting up a series choke....have had noise down to S4 on 20m....40m is still a problem though.

Bit the bullet and just bought an analyzer so I can once and for all get the antenna as resonant as possible.
Also got a manual tuner with some appropriate meters so I can keep an eye on operating conditions.
Have a new dipole going up in the morning. Did a very simple multi-bander for 10' 20' & 40m.

Feeling like I'm making progress.

Hi Macro,
One thing you might try is a loop antenna in the attic. If you can cut it for 40M it will work the higher harmonics fairly efficiently. The noise is almost surely coming from inside the house; though, as was said above. As an example, I have a back up HDD on my computer table next to the operating desk. The power supply for it was giving me almost the same noise you have. It stays unplugged now. Way back in HS my electronics teacher told me that the only to fight noise was at the source. Even if you have to hide a vertical by stapling it to a tree in your back yard, an antenna outside and away from the house will be more noise free and get out better. hth
73,
Rob

Antenna feedpoint, right below the 6:1 balun.

If you haven't already I'd find a battery to use temperately on your radio (I stole one out of our riding lawn mower) and flip your main breaker. After they got my powerline noise fixed (they found a lot) this spring I still had some noise they couldn't find. I did this with a battery and the rest of the noise was on my end. I tracked it down to a replacement power supply for my laptop. It was just about wiping out 20m and not doing 40m any good.

I am getting to this party a bit late, but, before I did much else, I would get the VOM out and check the continuity of the CO-AX and connectors to be certain that the center to center is ZERO ohms, shield to shield is ZERO ohms and the center to shield is INFINITE ohms and that it stays that way during manipulation of the connectors and CO-AX cable itself

As for the manual tuner:  Having a low SWR through a tuner doesn't tell you how much power is getting to the antenna, it is only telling you that the SWR might be low enough to keep you from smoking your finals from excessive DC current in your final amplifier.  The tuner may be transforming 100 watts with high SWR into 2 watts with low SWR.

I am old and my eyes are not as good as they once were and have been playing with this radio stuff for over 40 years and the photos of your antenna looks like green insulated wire connected to the center insulator and I would really like to see the solder joints from the antenna wire to the center insulator connections up close and personal.  From the view of your photo, something looks fishy.?

 
It looks like Budwig HQ 1 center insulators.  


http://www.universal-radio.com/catalog/antsup/1782.html

Well, that would pretty much catch the tuner on fire !!!  

Under most conditions, the tuner isn't going to be disipating a lot - maybe a dB on a bad day.

Here a nifty app that I use to determine tuner loss ======> Tuner_Thingy   I use the downloaded version.

Sorry OM, but, for some reason I do not see your photograph.

I would hope that the tuner didn't start on fire, although a piece of plywood I built a tuner on and used electric fence wire in the circuit and grounding started on fire back in the 1970's.  When I transmitted the circulating currents in the ground side got red hot and then sort of got weak and sagged down onto the plywood.  It only happened on voice peaks, but, I was running an E.F. Johnson Invader 2000 at the time at full output.  Luckily for me the smoke caught my attention before the flames did.  I have since upgraded the circuit with much larger diameter copper wire.

As for starting his tuner on fire, that depends on a number of variables that at this point seem undefined.

The one thing that I can say with 40 years in this hobby is this, "I suspect that the vast majority of antenna problems in existing designs that are having problems can be resolved with a soldering iron on the CO-AX and it's connectors.  Additionally, antennas installed near or on metal buildings will not work as well as first expected."

I really hope we get some feedback when this get figured out.  My curiousity is killing me