Ho

I've been HF mobile from my 04 Prius for a few years now and enjoy it tremendously. Here's my problem. I roof mounted my Screwdriver antenna and have discovered that the hand-wound matching coil is  getting buffetted by the wind, and, over time, the coil either breaks free or stretches and goes out of match. Anyone have any ideas about more mechanically solid options?

73

VE3XKD

I don't know. The antenna was tight, and I can see the gasket on the leftover mount part that is still attached to the mount. The temperature is going up this week to minus 1 C and I should be able to take it off and have a close look when i replace it.

Many thanks for all the pointers. I suppose 25 years of service is good enough from one antenna.

My neighbor is going to lend me his heated garage with the 12 foot ceiling so I can do the work.

Merry Christmas all!

VE3XKD

All

I had the unfortunate experience of my 25 year old Larson base coil shattering on me. I was driving into an underground garage and it was under construction and had lower than normal clearance at the entrance, I stopped, got out of the car, and twisted my Larson at the plastic base ad the whole thing shattered in my hand because the mount threads had corroded from all fo the salt the city spreads on the road here and the antenna had become stuck to the NMO mount. It was minus 15 C at the time. I was in a hurry and gave it my usual hefty twist to unscrew it and the plastic  just shattered.

I have a replacement Larson antenna, should I coat the mount threads with anything so this does not happen again.

Hi

I had similar problems with the COP on my Toyota Prius. I carefully wrapped each COP wire and connector in 3M 1181 copper foil tape, and wraped each COP wire back to  the engine chassis as far as i could go. I tack soldered the 3M 1181 seams, and bonded each line to ground. Eventually i cured most fo the noise, and now have only about S2 to S3 to contend with. there is some info on Alan's web site about using 3M 1181. Oh yes, each COP line has as many ferrite beads on the line as i could physically place.

If you are not certain where the noise is coming from, I suggest you make a 1 inch loop probe out of RG 58 or 59, attach the probe to your HF radio, and start listening or probing for the sources of noise. Once you locate a noise source you can either bond it or add ferrites or cover it in 3M 1181 and shield it.



Good luck!

Hi

I have a Hi-Q 3.5 short HF screwdriver centre-mounted on the roof of my Toyota Prius hybrid for the past two years. I find the installation works really well and I consistently get good signal reports. Monday evening  I worked the Azors on 20, and I generally have no problems working Europe. While roof mounting cuts down the length of the whip by several feet, and thus impacts efficiency, particularly for the low bands, I was able to add a Capacity hat and I manage to do fine on 80 meters. The problem with roof mounting is being able to re-enforce the roof so that the antenna will be sturdy. I managed, but it was a bit of effort.

Enjoy!

John VE3XKD

Ahhh

Been there, done that. I had the same intent for my Toyota Prius. The Diamond mount scratched the hatch paint and both the scratch in the car and the mount rusted after one year. The stubby antenna was not a great performer so I sold the mount and the stubby.

I ended up drilling holes, and center mounting the HF antenna in the roof after much labour, re-enforcing and effort.

However the results are worth the effort. As my teenagers say...Dad you have the coolest car around and it's neat to talk to those guys in Germany on the radio when driving us to school.....

After two months of winter, the installation works fine. The coldest has been minus 25  C. The only thing I don't do is keep the HF antena mounted as I am worried about salt spray damage, though VHF/UHF has been great all winter. It is also a pain to get the car into the garage with the HF antenna as there is not enough length in the garage, so I have not been doing too much HF mobile so far this winter.

cheers

Hi All

I am happily mobiling HF with my Prius (worked Florida on 40 last night), but winter is coming here in Canada e.g. last night was minus 8 C and its going to get really cold in a few months. Since I have my ICOM 7000 radio installed under the passenger seat and it is difficult to take out I was wondering if it is safe to leave it there during the winter when temperatures often go to minus 30 C or will there be damage from the cold/heat cycles if I try to operate HF mobile when the radio is cold?

Does anyone have any experience with rig failure due to extreme cold?

Hi All

I am happily mobiling HF with my Prius (worked Florida on 40 last night), but winter is coming here in Canada e.g. last night was minus 8 C and its going to get really cold in a few months. Since I have my ICOM 7000 radio installed under the passenger seat and it is difficult to take out I was wondering if it is safe to leave it there during the winter when temperatures often go to minus 30 C or will there be damage from the cold/heat cycles if I try to operate HF mobile when the radio is cold?

Does anyone have any experience with rig failure due to extreme cold?

Hi

My experience removing the headliner on a Toyota Prius to install an NMO and a re-enforced Breedlove mount for HF is that is a fairly easy job to remove the headliner, if you take your time and remember where you put all the screws and clips taken off for removal :-)) Just be patient when doing it. As I had a lot of work to do I actually drove around without the headliner or interior lights for about two weeks!

I found a description of how to remove the Prius headliner on the web. You may find a similar description for your car if you google it.

Good luck,

VE3XKD

I have successfully mounted the HiQ 3.5 'short' to the roof of my Toyota Prius using the Breedlove mount and by adding in additional Aluminum backing plates. I found I was able to slide and wedge the additional backing plates between the roof sheet metal and the supporting ribs. This works well, and I can 'shake the car' if I grab a hold of the mount. One caution, some roofs are  contoured so the backing plates should have a slight curve, and the corners should be ground down to provide less of a point so that one can avoid 'digging in'to the roof sheet metal when wedging the backing plates into location.

The roof mount works well for me, although the whip is a bit shorter due to the antenna being further from the ground, I made up for some of the length reduction by using a capacity hat on the Hi-Q. The strength of the modified mount  more than compensates for the added windload of the capacity hat.

Hi

Thanks for all of the information and research everyone has done. It seems that it is a Heathkit Noise Blanker, and at one time it was a mod for the Collins receiver, though not a popular mod, and there is no documentation of the mod that I can find on the web.

I hope to turn the radio on in after a few more days of cleaning, and will see what the mod does.

Hi

I recently bought a very dirty non-working Collins 75S 3C at an estate sale, Round Emblum, serial number in 30k range, and am in the process of cleaning it up. I noticed a rather unusual circuit board, 2 inches by 4 inches mounted below underneath the chassis. It has 2 coaxes going to VFO output phono jack, L3 and 1 going to a small pot mounted in the pre-selector bar assembly that moves the preselector coils up and down. There are 2 ICs on the board, an M 7720 and M 7707.  there is one part number on the board, 85-1412-3.

Can anyone help identify what this is?

Hi

for some reason, the design of the DC-DC inverter produces RFI from about 2.5 to about 15 MHz.
Suppression of the HF noise was difficult, I did some mods inside the DC-DC inverter(added filter capacitors and ferrites, plus a LOT of bonding and grounding. I'm not sure many hams would go to such extents. While there is still some RFI noise, it is down to abt 1 S unit, except for a short pulse type noise that appears every time the Electric motor kicks in. While i have some ideas on removing the residual noise, I am quite happy with the results so far. My coolness factor with my teenaged kids whent way up when I was having an 'Armchair copy' QSO with a Station in Munich while driving them to a friends house.

Moounting the antenna in the centre of the roof was a challenge, and involved drilling holes and removing the headliner to add in re-enforcing plates, but the results were worth it.  The antenna is a HiQ 3.5 with capacity hat and 5 ft whip. I sure get a lot of stares, mind you.

I have some Spectrum Analyzer screen shots that show the noise spectrum. With the roof mounted screwdrvier I have had no problem working DX on 20.

Eventually I'll get around to writing this up as an article that I can post to a web page.

Cheers