Amateur (ham) Radio in a TDI

Personally I would have made it black. 99% of people aren't going to notice it at all though.

In other news, my AM radio wire worked. I put a long piece of thin wire under the trim on the roof (Mk4) and it picks up AM well enough that I can listen to a traffic report now. It's not great, but it works just enough that I'm not going to knock myself out trying to make it any better.

I have another plate that I'll paint black and see how it looks this weekend. I think it'll look better.

So, I'm finding that my Mk4 produces a lot of interference on 2m. I've done some testing with a handheld radio and it picks up the same interference as the mobile unit. So a better mobile unit is likely not the solution. It also isn't coming through the power connection to the mobile unit, since the HT picks up the same noises with no physical connection to the car.

It's bad enough that it desensitizes the receiver so some repeaters will cut in and out if the motor is running. When I turn the motor off, it's crystal clear.

UHF is fine.

Unfortunately I think this is a difficult problem to solve. The car is emitting RF, and the radio receives it, like it's designed to do.

I believe most of the interference is actually coming from the CAN bus or whatever system the various modules use to talk to each-other. I can hear changes in the noises when I do things like open a door, or the rear hatch. Sounds like digital communication type noises.

Is this typical of a Mk4? Anybody else notice this? Are they just a big rolling source of VHF interference?

Had a 2000 Jetta TDI Mark IV for 327K miles of mobile operation, and found it to be extremely RF quiet on 160-2 meters. VHF antenna was initially a mag mount 1/4 wave and later a 5/8 or 1/4 wave whip on an NMO mount between the moonroof and windshield. There were some low-level spurs on 10 and 15 meters when I turned the taillights on, but since those are generally daytime bands it was a non-issue. Only RF issue was if I transmitted on 40 meters with more than 30 watts, it shut down the cruise control. Antenna was a KJ7U screwdriver mounted off the rear tow ring.
My 2009 TDI Jetta generated a lot of garbage, particularly on 20 meters, from the car's electronics. That one just went away in the buyback, and my replacement is a 2005 Mark IV that so far seems as RF quiet as my 2000 model. 73 de AA1K.

Hmmm, it's interesting that your 2005 is RF quiet. It shouldn't be much different from my 2004.

The only thing I can think of is that mine is a fully loaded GLS model, so it might have different control modules. For example, it has ESP, which not all cars of that age would have.

I've thought about putting RF chokes on all the wires leading to any control modules. It would be a bit of a job locating them all, I guess.

What kind of transceiver are you using?

I found the source of the RF interference! It's my dash-cam, which starts and stops with the engine.

So that narrows the problem down considerably. First thing I'm going to try is a ferrite bead on the USB cable that powers the camera.

UPDATE:

Since the dash-cam uses a mini-USB plug as it's power source, I just grabbed a cable that already had a ferrite bead on it, and connected it to a portable battery-powered USB power supply. The unwanted interference was virtually eliminated!

I can still cause the interference by holding the camera beside the antenna, on the roof of the car, but when it's installed in its normal position in the car, at the top of the windshield, the interference is gone. Woo hoo!

The cable that was supplied with the camera is quite long, and has no ferrite bead. The cable I was testing with isn't long enough for proper installation in the car, but I should have no trouble finding one that is, and has a bead on it.

Power is coming from an unused circuit on the fuse panel, stepped down to 5V for USB. I'm going to get a better quality 12V to 5V USB power adapter and a cable with a ferrite bead on it. Hopefully my troubles will be over.

For the curious, this is the camera I'm using: http://www.gearbest.com/car-dvr/pp_142025.html

Hello,

I changed to a black base:





I like it better. Someone asked if it was a magnetic mount. I guess it looks like one... just with no wire.

Scott

Does it whistle much at highway speeds?

Not that I can tell. I drove with the windows down this morning to take a better listen. I didn't hear anything but the sound of my tires and traffic around me. My windows go up once I'm past 50 mph.

Mine whistled very loudly. I could hear it with the windows up. I wrapped the antenna in a stretchy self-adhesive silicone tape, and that helped a lot.

This stuff: http://www.princessauto.com/en/detail/magic-wrap-tape/A-p0700353e

So, now that I've caught the ham radio bug again (been licensed for about 27 years, but not very active for the last 25), in addition to my mobile unit for voice, I've started playing with APRS (position reporting through packet radio).

I'm using a Mobilinkd TNC which is a KISS mode TNC that connects with Bluetooth to an Android phone or computer.

Originally, I had the TNC connected to a handheld Baofeng UV-82, but I've found, not surprisingly, that an HT inside a car is useless. Doesn't receive much, doesn't transmit far.

So, I made a cable to connect my mobile rig to the TNC and that gets out really well. Digipeaters as far as 50 miles away have received my packets. My mobile only puts out 10 Watts.

Since that worked really well, I ordered a Kenwood TM-281a which is a basic 2m rig that puts out 65 Watts. I plan to mount that in the rear for packet only. I'll need a second antenna...

Some options I'm tossing around for the second antenna include:

1. Another hole in the roof, with an NMO mount and a 1/4 wave whip. I'm a bit worried about having two antennas of the same band on one roof. I understand that I probably need to have them at least 19" apart (1/4 wavelength).

2. Install my roof-rack and screw or weld (I have access to a TIG Welder) a small flat plate where I can put an NMO mount. If I put the antenna on the front roof rack that would give me better separation from the antenna in the rear. I'd be stuck with always having a roof rack installed.

3. Glass mount on a side window. I think it would look ugly. I'm not sure if my windows would be compatible with a glass mount. Some tinted windows block the signal.

4. I have a mag mount that I could put on, but I hate them, and the cord running across the roof looks ugly.

5. Some kind of lip mount antenna, but on a Golf I'm not sure where I could put it. Would also look weird and ugly.

I'm thinking option 1 is the best, although it does involve drilling a hole in the roof.

I had this setup on my Mk3 at one point:



There was certainly more than 19" between my FT-857D and APRS antennas. My FT-857D eventually developed a desensing problem which was eventually repaired (blown diodes, I think). I wouldn't do another setup like that unless I could put one antenna on the roof and the other on a lower platform like a trunk lid (not an option on a Golf). If APRS is only a temporary need, I might consider putting a small unit inside on the dash for a day. It's not ideal, but it could work if your coverage is good.

These days, if I "need" to use APRS, I transmit my position with either the APRSDroid app or I send it via D-STAR.

Good Luck,

Scott

Yeah, I'm sort of re-thinking whether I want to permanently install an APRS system.

I think it would be very useful for long road trips, especially into wilderness areas, of which there is plenty of around here (with a sprinkling of digipeaters and igates, no cellular service though). Also, my brother has a boat and I go out with him sometimes. Having APRS in a boat would be great, in case of emergency.

My mag-mount antenna is probably the way to go if I just want to pop it into my vehicle, or someone else's during a trip.

Although I hate the idea of mag-mount antennas, I tested out the one I have with my new Kenwood TM-281A and wow, it was actually great! I was playing with it in the house, so I just stuck it on a cookie sheet, knowing it needed some metal under it for a ground plane. SWR was 5:1...no good. Then I grabbed an aluminum crutch that was in the corner of the room (a souvenir of my knee surgery last year) and put that underneath the cookie sheet. SWR dropped to basically 1:1 in the middle of the band (The needle didn't move. I couldn't even say it was 1.1:1...thought something was broken). At the edges of the band it was 1.3:1. Still really good. So that mag-mount antenna seems to work very well, as long as you put the right thing under it! Hopefully a car under it will do the trick.

The SWR/Power meter showed 25 Watts output on low, exactly what the manufacturer specifies for the radio, so that suggests the meter is reading correctly. I didn't try high-power because I didn't think my power supply was up to snuff for that.

So, for now, I guess I'll use my much-hated, but apparently awesome, mag-mount antenna.

Hello,

Today I took some photos with each of my antennas mounted: From left to right - Least obnoxious/effective to most obnoxious/effective.



CLICK HERE for a larger view... I'd have to be really intent on high-performance comms before I'd drive around with that big thing on the car.

Scott

Nice. The big one looks hilarious. I guess if you were in a remote area you could install that one for stationary use.

So a quick question, has anyone installed an antenna in the center of the roof with NMO mount on a MK4 Jetta with sunroof? I am wondering if there is enough clearance or not? I never looked at the sunroof open without headliner, but it seems those NMO mounts with the 90 degree cable exit might just work.

I even consider it until after the headliner is out and you can see with your own eyes what kind of clearance is under there. I think most who've drilled into the roof have done it well aft of the retracted sunroof. You also have to be aware of the cross-member locations. Good Luck!

Good point about the cross members. I will drop the head liner soon to repair the sagging fabric and will do my own evaluation, but I was just wondering if anyone had first hand experience.

Sent from my XT1575 using Tapatalk

NMO with sunroof

Has anyone dropped their headliner to see what the clearances are like with the crossmembers and sunroof/moonroof?

On my 2000 Mark IV, I installed an NMO mount in the roof just in front of the sunroof. Access was through the control area. I drilled a small hole and then expanded with a Greenlee chassis punch, which made a nice clean cut. I snaked the feedline down through the passenger side pillar behind the windshield; no air bags there on this year's model.

I used a 2-meter 5/8th wave whip on this mount and it worked quite well. When I sold the car, I removed the whip and covered the mount with an NMO cap.

I also had an HF screwdriver antenna mounted off the rear, using a homebrew bracket attached to the tow ring.

Now I have a 2004 Mark IV but haven't drilled any holes yet. Mounted an HF whip on the roof rack, which I leave on the car all the time, and use a magnetic mounted dual-band whip for 2 meters and 440.

73 de AA1K

Building up courage for an NMO mount in the middle of my roof on my '03 Jetta, no moonroof. Taking out the headliner looks to be a PITA. Has anyone drilled the hole and snaked the coax through without removing the headliner?

Dave
ai6vx

You should consider at least lowering one side of the headliner so you can see where your roof's crossmember runs. It sure would suck to pick a great-looking location, drill, and then discover that you're in a structural piece.

With one side lowered even an inch or two, you can then reach in with a coat hanger to grab the coax at your hole.

Good Luck,

Scott

The headliner is not that big of a deal to remove. Just make sure you understand the process, have the required tools handy (which are minimal), and take it slow. I would recommend dropping it whole vs just one side actually, since it's not that much more work, and you reduce the likelihood of kinking the headliner.

Unlocked Kenwood D710G w/Bluetooth Module wired to TNC for AprsDroid OSM.. Comet CA-2X4SR antenna mounted to FrontRunner Antenna mount on a FrontRunner Rack.

I just installed an NMO mount on my 2019 eGolf. Took me a long time to get the courage, then spent over an hour today popping off trim to see where it should go and still clear everything. In the end, I popped out the overhead lights for the rear seats, and then with a camera on a stalk, saw how to route the cable. Very careful measurements later, and it was time to drill. Snaked the cable over to the B-pillar, behind the air bag curtain, and right now it exits at the base of the B pillar. I still need to run 12V over but I'll be using my Yaesu FTM7250DR.

emshamguy said:

NMO with sunroof

Has anyone dropped their headliner to see what the clearances are like with the crossmembers and sunroof/moonroof?

Click to expand...

Old message, but I added an NMO mount to my 01' Beetle with sunroof. Did it just behind the sunroof and there was just enough clearance that the sunroof still works without running into the NMO mount or the cable. What sucks on the Beetle is the roof isn't flat - it's rounded enough that an NMO antenna doesn't sit flat to keep the water out. I had to use an NMO gasket to take up the gap.

Nice work! I couldn't recall if I had shared my Mk7's ham radio install, not in this thread, anyway. Here's a quick overview, if there's such as a thing with my car: It's not a TDI, but may give some ideas for some of you...



With a steering wheel desk for hand-logging and a passenger seat desk for the laptop...


Under the trunk floor...


The Breedlove mount was causing problems on UHF. So, I replaced it with this combination mount by Electro-Magwave. Not only does it have an NMO mount, it also restores the GPS signal to the compass and clock that was lost when I removed the original sharkfin antenna...


Here's my HF solution, a Scorpion SA-680BW...




I recently built a "rear seat delete" with forced ventilation for the equipment area. It does a good job of vacating heat from the one cubic-foot equipment space...




The car looks like this most of the time...


73,

Scott, KE4WMF

Stealth TDI said:

Nice work! I couldn't recall if I had shared my Mk7's ham radio install, not in this thread, anyway. Here's a quick overview, if there's such as a thing with my car: It's not a TDI, but may give some ideas for some of you...

With a steering wheel desk for hand-logging and a passenger seat desk for the laptop...

Under the trunk floor...

The Breedlove mount was causing problems on UHF. So, I replaced it with this combination mount by Electro-Magwave. Not only does it have an NMO mount, it also restores the GPS signal to the compass and clock that was lost when I removed the original sharkfin antenna...

Here's my HF solution, a Scorpion SA-680BW...

I recently built a "rear seat delete" with forced ventilation for the equipment area. It does a good job of vacating heat from the one cubic-foot equipment space...

The car looks like this most of the time...

73,

Scott, KE4WMF

Click to expand...

Holy smokes! Nice install! Very clean and organized. I have yet to buy a removeable head rig - I should have gotten the FTM-400DR when they first came out as they were selling for less than $400 then. Now everything has gone up a lot in price.

I recently, approximately 2 years ago, got my ham license. Then about a year ago inherited my 03 golf tdi when my brother passed away. I have recently been thinking about an antenna and radio for it. I never thought there would be so many hams on here. Thanks for some good ideas!
Aaron KJ7CHW

So we have another wildfire in So. Cal. Alisal fire, just north of Santa Barbara and ~10 miles from where I work. Been enjoying having a 2 way radio in my beetle and e-golf. The local ham radio folks have better information on the fire vs TV and radio news stations. With ADSB, the can even watch and report on air support.