Ham Radio Interference

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linw

2849 posts

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#173339 20-May-2015 08:49

Wonder if anyone has some good advice for my 80 year old friend across the road. His next door neighbour is a radio ham and has a hulking great tower aerial 20 metres away from my friend. When there is a transmission it obliterates radio reception and phone for my friend.

An inspector has been up and says the signal is within legal limits, but, funnily, when this happens, there is no interference. But when the inspector has gone, guess what, interference resumes.

Friend has been putting up with this for about 15 years and his health is such that he doesn't need the phone to be out. The ham has been approached numerous times to no avail.

I am just across the road but, luckily, don't get this interference (did about 20 years ago).

To me, the different results with inspector there and not there, suggests an amplifier can be switched in and out. But how could one get cut and dried evidence of that?

Could one hire an accurate field strength meter that would produce actionable evidence? The inspectors must have one but they wouldn't like to lend it!!

Just looking to see if someone has some friendly advice.

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#1308157 20-May-2015 08:52

You need an RF sweep generator ;)

kiwiharry

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#1308172 20-May-2015 09:09

I received this in a newsletter from Radio Spectrum Management in March 2014. Maybe see if this service is an option, although it looks like it relies on cellular service, so if the fault is as you describe, then it could jam the monitoring connection too.

http://createsend.com/t/r-C8AE485FAEE8CECD2540EF23F30FEDED

Another tool in the Radio Inspector’s kit A noted characteristic of interfering radio signals is that they have a lot in common with toothache – when someone is in position to examine the problem, it temporarily disappears. Advances in computer-controlled receiver technology and in the capability of cellular networks have enabled RSM to successfully trial remote-control of a radiocommunications receiver, enabling detection and measurement of radio signals at a distance. The Radio Inspector no longer needs to remain in the vicinity of the receiver, which can be set up to record signals or to provide real-time monitoring, with control of all receiver parameters from a distance. This provides new efficiencies, particularly in regard to reduced travel, and the opportunity to investigate radio signals. RSM is looking to extend this ability over time.

If you can't laugh at yourself then you probably shouldn't laugh at others.

knoydart

904 posts

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#1308243 20-May-2015 10:20

I suggest you log another call with RSM on 0508 RSMINFO. The RI should re investigate this matter as it sounds to me like another visit might be in order. Otherwise drop an email to info [AT] rsm.govt.nz with your concerns. I would suggest PM me the details but I'm not a trusted user for RSM on here.

regards

Pete

psychrn

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#1308254 20-May-2015 10:32

Ive asked a Radio Ham friend of mine his views. Be interesting to hear what he comes back with ??

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linw

2849 posts

Uber Geek

#1308259 20-May-2015 10:43

Thanks for input so far, guys. I am in a bit of a delicate position not being the complainant but let's see how we go.

@kiwitrc - presume you mean a very powerful one pointing at the aerial?!

kiwitrc

4123 posts

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#1308261 20-May-2015 10:51

linw: Thanks for input so far, guys. I am in a bit of a delicate position not being the complainant but let's see how we go.

@kiwitrc - presume you mean a very powerful one pointing at the aerial?!

Doesnt have to be powerful :)

nzlegs

52 posts

Master Geek

#1308334 20-May-2015 11:34

Would be interested to know what equipment the alleged interference is being received on. I once had the unfortunate experience of not only being the perp but also the victim of radio interference.

The equipment suffering the interference was a 'staff' television set in the staff cafeteria. The equipment causing the interference was a trigger transmitter in the 'front office'. Part of a 'base station' radio set used to communicate with workers out in the field. This was happening in several towns in Northland.

The cure (and it was upto me, being the resident tech) was to fit filters to the TV sets. They were built to a price and had inadequate aerial filtering.

As a radio ham, running an AX25 BBS, that also caused alleged interference to a neighbour about 4 or 5 houses away.
He was running 2 TV sets off of 1 aerial via a splitter amplifier. In this case, it appeared that the splitter was generating the interference. Again, a filter on the splitter fixed this problem. Closer neighbours were not affected by the operation of the BBS.

I should also mention that I was in communication with the Radio Inspectors during this.

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linw

2849 posts

Uber Geek

#1308786 20-May-2015 20:11

The equipment was a copper landline phone that had bad interference that made it unusable and a stereo that couldn't be used for radio or CD play.

The 'perp' has tried to wrap cables around a ferrite core but it was ineffective.

richms

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#1308790 20-May-2015 20:15

For it to mess up a CD player then it is probably well over the legal exposure limits.

Or its a dirt cheap not meeting any standards piece of rubbish CD player.

Bit hard if the perp sees someone come to measure strength and dials it back heaps.

Richard rich.ms

nzlegs

52 posts

Master Geek

#1308826 20-May-2015 20:28

What radio frequency is that equipment on because the radio inspectors only worked with interference to radio equipment.

Interference to equipment that was not radio equipment was caused by that equipment receiving (and rectifying) radio signals. IE the fault is in the equipment being interfered with.

Stereo equipment has speaker leads that act like aerials and telephones have a peculiar habit of being connected to long telephone lines. Also good aerials.

Jase2985

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#1308827 20-May-2015 20:29

is it a regular occurrence? like same time every week/night?

maybe get the inspector over if it is regular, but dont let the other person know and measure from your friends place, if it is indeed a strong signal they shouldn't have issues measuring the signal.

Aredwood

3885 posts

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#1308829 20-May-2015 20:33

Try plugging the phone into one of those ADSL filters. As they are designed to block high frequencys. I'm guessing it is a simple wired phone and not a cordless phone.

Do you still get normal cellphone reception and call quality when the neighbour is transmitting? If not then complain to the cell phone network as well.

richms

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#1308857 20-May-2015 20:57

There are still maximum levels of the field strength that they can put out, and they are not actually that high.

Richard rich.ms

linw

2849 posts

Uber Geek

#1309249 21-May-2015 13:23

He could have problems with phone/spkr wiring 'aerials' but the crux is whether there is interference when the perp is doing a test transmit for the Inspector. I don't think he transmits on a reliable schedule to enable a sneaky monitor.

His phones have ADSL filters.

Anyway, think knoydart's advice to re-contact the RSM people is the best option so have told my friend to give that a go.

Also, mentioned that bolt cutters on the feed cables would work well!!

Fred99

13684 posts

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#1309288 21-May-2015 13:46

My father was a radio ham - and had issues with TV interference with neighbours on more than a few occasions. Mainly his fault I expect. That was in the days when most hams made their own gear, lord knows what the RF exposure levels were in his "shack", but as kid I thought it was pretty cool being able to light up fluoro tubes without connecting them up to anything.
IIRC there was a meter (SWM = standing wave meter?) connected up to the tuning coils before the antenna, high (standing wave) level indicating that the whole rig was off-tune a bit and probably generating interference, so I suspect he had a pretty good idea when he might have been causing those issues, but sometimes carried on regardless when work may have been needed on the antenna itself.
But I'm also pretty sure that we had complaints about interference at times when for one reason or another he wasn't transmitting at all, broken equipment not being used until it could be fixed etc etc. Of course he was indignant in those cases.

Pinned on the wall was a letter from Washington, ticking him off rather formally for transmitting in some frequency band used by the US military - probably a generous gesture by them tracking him down via his call sign and send the letter - rather than just dob him in to NZ authorities.
Over the years there were a couple of incidents with (unbalanced) people in the neighbourhood suggesting that he was spy. Then others accusing him of being a traitor to humanity - following publication of a book ("Harmonic 33" by Bruce Cathie ???) which "exposed the fact" that the then quite commonly seen "cubical quad" ham antenna was a device used to communicate with aliens. Not idle gossip, but formal complaints laid with police, good folks performing their duty to keep us all safe.

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