# Radio interference - Xmas? **URL:** \ **Category:** emonTx\ **Tags:** radio\ **Created:** [14 December 2019 16:39 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736 "2019-12-14T16:39:51Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [16 December 2019 19:51 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/21 "2019-12-16T19:51:13Z")
> [@Bill.Thomson](#): > > mount it further away from the wall _if you can._ I realize that may not be practical/possible. I could fashion a stand-off out of something or other I’m sure. How long should it be? > [@Bill.Thomson](#): > > move it away from the wire bundle it’s adjacent to. > _That’s_ a definite detuner / radiatiion pattern modifier. That’s the mains supply to the house, FWIW. I could move it out onto the ply to the left of the picture. Again, how far? > [@Bill.Thomson](#): > > bring the feedline straight out from the elements, i.e. perpendicular to them, > for a distance equal to, or greater than, the length of one element. Ah, OK. That’s definitely doable. Many thanks, Dave ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [16 December 2019 19:57 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/22 "2019-12-16T19:57:31Z")
Rule-of-thumb is one-quarter wavelength (or more) separation distance. (roughly the length of one element) One-half wavelength or more is better but if that’s not possible, quarter-wave separation is better than nothing. So mount your dipole as high and as far away from the wall and mains cables as practical. ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [16 December 2019 19:59 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/23 "2019-12-16T19:59:55Z")
> [@Bill.Thomson](#): > > So mount your dipole as high and as far away from the wall and mains cables as practical. OK, the mains cables take a right angle above the picture and run above the antenna, towards the south/left. I suppose I should stay half-wave below that. ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [16 December 2019 20:01 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/24 "2019-12-16T20:01:06Z")
> [@djh](#): > > I suppose I should stay half-wave below that. Correct. ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [16 December 2019 20:01 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/25 "2019-12-16T20:01:51Z")
Only one of the dipole elements radiates energy. _Ideally_ you want that one on top. So you can try flipping it end for end. It may or may not make much, or any, difference, but it’s easy to do. ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [16 December 2019 21:09 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/26 "2019-12-16T21:09:00Z")
> [@djh](#): > > I could fashion a stand-off out of something If you can, mount the antenna from the center vice the ends of each element. ---
**Author:** ![borpin](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/borpin/32/193_2.png) [@borpin](https://community.openenergymonitor.org/u/borpin)\ **Post date:** [17 December 2019 05:58 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/27 "2019-12-17T05:58:00Z")
This thread may be of interest as well. > [@Improving RF signal strength emonTH emonTX](https://community.openenergymonitor.org/t/improving-rf-signal-strength-emonth-emontx/5318): > > Probably one for @Robert.Wall but does the gauge of the EmonTX/TH antenna affect its signal strength? (I know it’s length needs to be fairly precise). I’ve moved my base station, and trying to improve their signal strength. Paul ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [17 December 2019 10:54 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/28 "2019-12-17T10:54:21Z")
Yes, I’ll perhaps add a length of timber batten to a block of wood. Fasten the block to the wall and the centre of the dipole to the batten. I’ve been wondering whether adding a reflector behind it would help - I started out thinking yagi-type reflector, then old satellite dish and finally Brian’s ali foil stuck to cardboard 🙂 ? I think I’ll also need a directional antenna if my RTR-SDR is to be of any use. It seems to come with telescopic dipoles. Any thoughts? ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [17 December 2019 12:25 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/29 "2019-12-17T12:25:01Z")
_does the gauge of the EmonTX/TH antenna affect its signal strength?_ Although it was Paul Reed who asked the question quite some time ago, I’ve answered it here for reference. The larger the diameter of an antenna element, the more _broad-banded_ it tends to be. It’s one of those things that’s of interest when an antenna is used on more than one frequency. Since any given OEM transmitter isn’t intentionally operated at anything other than its assigned frequency (save for drift, which can be ignored) the gauge, or diameter, of the radiating element will have minimal effect on antenna operation. (within reasonable limits. i.e. if the element is made _much_ larger, the effect will be noticable or even significant) ---
**Author:** ![borpin](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/borpin/32/193_2.png) [@borpin](https://community.openenergymonitor.org/u/borpin)\ **Post date:** [17 December 2019 12:36 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/30 "2019-12-17T12:36:46Z")
> [@djh](#): > > Brian’s ali foil stuck to cardboard Definitely not mine - never did understand any of this stuff 😀. ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [17 December 2019 12:53 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/31 "2019-12-17T12:53:26Z")
> [@djh](#): > > I’ve been wondering whether adding a reflector behind it would help It would, but the addition of said element involves more than just hanging another element or foil-covered sheet of cardboard behind the radiator. The length of the reflector as well as its spacing from the driven element are fairly critical dimensions. If either is off by more than a few percent, performance usually suffers vice improves. At 433 MHz, it’s fairly easy to be off by those “few percent,” unless care is taken to ensure accurate measurements. > [@djh](#): > > I started out thinking yagi-type reflector, That’s the correct line of thought. In addition to a reflector, a director or two ot three would also improve performance. Adding parasitic elements (reflectors and directors) increases effective radiated power, but at the same time decreases _beamwidth_ which means the direction the antenna is pointing becomes important. So it’s a tradeoff between gain and beamwidth. Considering the typical distance between OEM “transmitters” and “receivers” it’s not likely to be a problem unless the antenna has more than 10 or 12 elements. In a nutshell, you’d might be better off buying a UHF Yagi of the kind typically used on the 440 MHz Amateur Radio band. > [@djh](#): > > then old satellite dish To be effective at 433 MHz, it’d have to be _much_ larger than the typical “satellite dish.” The satellite downlink frequency is ~2 GHz, which is why the antennas can be comparatively small. > [@djh](#): > > ali foil stuck to cardboard The foil-on-cardboard method is aimed at _monopole_ antennas. Your dipole doesn’t need a groundplane. That’s the function of the second element. > [@djh](#): > > I think I’ll also need a directional antenna if my RTR-SDR is to be of any use. Quite the opposite, actually. You _want_ to be able to receive signals fron any direction. At this point, you simply want to know _is any interference present?_ If, at some point later you want to _locate_ said interference, then yes, a directional antenna would be needed. ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [17 December 2019 13:00 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/32 "2019-12-17T13:00:34Z")
> [@borpin](#): > > Definitely not mine - never did understand any of this stuff Ah, sorry. It was Paul Reed. ---
**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\ **Post date:** [17 December 2019 13:02 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/33 "2019-12-17T13:02:43Z")
> [@djh](#): > > Brian’s ali foil stuck to cardboard That reminded me of this, from [a UK aerial supplier’s website](https://www.aerialsandtv.com/lookattheothers.html): > Even crappy [Bacofoil aerials](https://www.aerialsandtv.com/aerials.html#PictureOfCheapoXBeam) come with instructions, in fact, because they’re aimed at DIYers who, the manufacturers assume, don’t know anything about aerials, they’re actually more likely to come with instructions. It’s that very ignorance that said manufacturers rely on to sell products which are, well, made of Bacofoil. Off-topic a little I fear. ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [17 December 2019 13:08 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/34 "2019-12-17T13:08:56Z")
> [@Bill.Thomson](#): > > At this point, you simply want to know _is any interference present?_ No I want to locate the source. Simply knowing it is there doesn’t help me at all. Obviously it’s a necessary step, but not worth setting up a specific test for. In the good old days I would have looked for a null with a radio that used a ferrite rod. Or what about a loop antenna? Ah, [https://www.instructables.com/id/Yagi-Antenna-for-the-70-Cm-Band-430-440-MHz-by-F4H/](https://www.instructables.com/id/Yagi-Antenna-for-the-70-Cm-Band-430-440-MHz-by-F4H/) ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [17 December 2019 13:13 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/35 "2019-12-17T13:13:36Z")
> [@djh](#): > > No I want to locate the source. Then you’ll want both types. The omni to determine _if_ you _have_ any QRM, and the Yagi to _locate_ it. > [@djh](#): > > [https://www.instructables.com/id/Yagi-Antenna-for-the-70-Cm-Band-430-440-MHz-by-F4H/](https://www.instructables.com/id/Yagi-Antenna-for-the-70-Cm-Band-430-440-MHz-by-F4H/) That’s the ticket. If you search for “build a 440 Yagi,” you’ll find _lots_ how-to info. Excercise care with measurements and you should be able to build one that works well. Here’s another link: [Ultra Cheap 440 MHz HAM Radio Yagi | Shawn Garringer's Website](https://www.shawngarringer.org/ultra-cheap-440-mhz-ham-radio-yagi/) ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [17 December 2019 13:26 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/36 "2019-12-17T13:26:09Z")
> [@djh](#): > > radio that used a ferrite rod Ah yes, the AM broadcast band. They operated from 535 to 1700 KHz (US, don’t know about the rest of the world) > [@djh](#): > > what about a loop antenna? It _can_ be done, but loops, like the loopstick, are typically used at MF/HF vice V/UHF. > **[Copper%20Loops%20For%20222%20and%20440MHz.pdf](https://www.iz3mez.it/wp-content/library/appunti/Copper%20Loops%20For%20222%20and%20440MHz.pdf)** ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [17 December 2019 13:33 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/37 "2019-12-17T13:33:07Z")
> [@Bill.Thomson](#): > > It _can_ be done, but loops, like the loopstick, are typically used at MF/HF vice V/UHF. > > [iz3mez.it](https://www.iz3mez.it/wp-content/library/appunti/Copper%20Loops%20For%20222%20and%20440MHz.pdf) > > ### [Copper%20Loops%20For%20222%20and%20440MHz.pdf](https://www.iz3mez.it/wp-content/library/appunti/Copper%20Loops%20For%20222%20and%20440MHz.pdf) That looks like a project for the next millenium! I think I’ll stick to the Yagi. ---
**Author:** ![Bill.Thomson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/bill.thomson/32/1834_2.png) [@Bill.Thomson](https://community.openenergymonitor.org/u/Bill.Thomson)\ **Post date:** [17 December 2019 13:35 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/38 "2019-12-17T13:35:21Z")
> [@djh](#): > > I think I’ll stick to the Yagi. If I were going to make one, I think I’d try the broomstick ultra-cheap antenna I linked to in post 34. ---
**Author:** ![djh](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@djh](https://community.openenergymonitor.org/u/djh)\ **Post date:** [31 January 2021 09:03 UTC](https://community.openenergymonitor.org/t/radio-interference-xmas/12736/39 "2021-01-31T09:03:43Z")
Been a while since I posted about this, but I just had an epiphany. ![Screenshot_2021-01-31 Emoncms - graph](https://community.openenergymonitor.org/uploads/default/original/3X/7/9/79c0836010e3de10c64105c9e74886ce4db7acb3.png) The blue line is the emonTx in the garage. At 08:21 I returned from buying my Sunday paper and parked the car. A few minutes later I looked at this graph and went out and re-parked it somewhere else. Perhaps the most interesting thing is that it spent the entire night and previous day parked roughly where I first parked it this morning, just facing the other way. The joys of radio transmission! [Previous page](https://community.openenergymonitor.org/t/radio-interference-xmas/12736.md?page=1)