Antenna Selection for Rovers

Antennas can be one of the most challenging and controversial aspects of roving. It all depends on your location, population destiny, terrain, bands and what you want to accomplish.

• If you plan to rove relatively near to high ham population areas and know of good operating locations then omnidirectional antennas work fine.
• If you plan to rove on the fringes of civilization then you may need more gain from your antennas.
• If you plan to operate while in-motion (with a driver buddy at the wheel) then you'll be interested in the omnidirectional antennas and/or limited turning radius directional antennas with a rotor.

Its recommended that you start your roving career located near high ham population areas so as to not get totally discouraged and experience what it takes (in terms of equipment and operator experience) to make QSOs from a rover.

The "Dish" Bands (5, 3 cm and 12 mm) are dominated by dish type reflectors with varius feeds:

Several vendors sell both the dish reflectors and single / dual band feeds. More information here.

There are many DIY instructions available for conversion of these satellite TV dishes for 10 GHz use.

• Check out K0AWU/s DSS feed here.
• W1GHZ 10 GHz link here.

The "Looper" Bands (33, 23, 13 and 9 cm.) are a challange for cost effective rover antennas:

Regular Yagis are available for the 33 and 23 cm bands but loop Yagis are feasible stating with the 33 cm band. Either will give you good results with relatively high gain for 6' long booms. "H" frames are popular for mounting multiple loopers onto a single boom. Transmission feedline losses become significant at these frequencies so use good, short feedline or you will have wasted your investment in a good antenna.
More loop yagi information here.

The "Yagi" bands (2, 1.25 and 0.7 meters) offer many alternatives for effective rover antennas:

Over the years I've tried many different antenna designs for these bands.

For local use horizontally polarized, omnidirectional antennas can work fine and have the advantage of not being directional (you don't have to aim them).

However, as you begin to venture away from ham population centers you'll usually need a directional antenna in order to work the more distant and/or weaker stations (and point away from local noise). The Yagi is one of the most popular antenna designs for these bands. It's available in narrow, wide and multiple band designs.

The log periodic Yagi is a medium-gain, multi-band antenna requiring minimum mast space. That is, you can have multiple bands on a single antenna boom.

Single band Yagis are also popular rover antennas offering higher gain per band. There are many DIY designs on the Internet as well as commercial kits available.

• More information here.
• DIY information here.

The Quad is another popular roving alternative that can be made into single or multiband versions. The gain is similar to Yagis but the winload and mechanics are more challanging.

The 6 meter band is one of the more difficult bands for an effective rover antenna:

• The physical size of an effective 6 meter antenna can be overwhelming to mount onto a rover vehicle.
• Taking advantage of the horizontally polarized "ground bounce" and reducing the atmospheric noise arriving from high radiation angles requires that the average height of your antenna one wavelength or more. This can be difficult to achieve on a rover vehicle.
• Pointing away from local noise sources (power lines, buildings, etc.) requires a good front-to-back ratio which also adds to the size of an antenna.
• Wind loading and additional weight (at the top of your mast) may over stress your mast when traveling at high speed.

Any antenna is better than a dummy load so go out and try something so that you have a point of comparison. Even a vertical will give you some contacts with the locals.

Over the years I've come to appreciate two types of horizontal antennas for 6 meter roving:

• A one to three element quad antenna has a narrow physical width, lower noise sensitivity and forward gain (with 2 - 3 elements) when in a "quad" configuration.

• The stressed moxon antenna is a good compromise with a low weight and wind load together with forward gain.

Note that you must properly decouple the feed line for best results with both of these 6 meter antennas. Higher is better!

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Coaxial Cable Management for Rovers



Coaxial cabling can be bulky, heavy and lossy.

Problem: During my Jan. 2011 rove the antenna crosstalk from 6, 2, 1.25 and/or 0.7 meter 100W amplifiers managed to zap my Yaesu FT-857D causing a $300 repair and took out the pre-amp of my external 0.7 meter amplifier.

Solution: During the January 2013 rove I tried to manage the antenna crosstalk and cabling issues by implementing a simple multiplexing arrangement. Rather than separate LMR-400UF individual cables for each of the 4 bands, I shared a 22 ft. LMR-600UF cable for all 4 bands. This was possible through the use of two, 4 pole Transco coaxial relays.











Loss Reduction Calculator: At 432 MHz my 22 ft. cable attenuation was reduced from 0.7 to 0.4 dB (not including connectors) for a savings of approx. 0.3 dB on 70 cm.

Weight Reduction: Four, 22 ft. LMR-400UF cables weigh 6 lbs. versus one 22 ft. LMR-600UF cable weighs 2.9 lbs. plus one 4-pole relay weighing 0.8 lb. = 3.6 lb. for a savings of approx. 2.4 lb. (not including connectors).

Bulk Improvement: Routing 4 separate LMR-400 cables down the telescoping mast with sliding antenna booms is a real headache. They end up catching the yagi elements and shorting out the RF capture areas when the antennas are "nested" (mast retracted).

Related Issues: (the devil is in the details)

- Coax relays can be sensitive to weather when use in outdoor environments. Up to 90 MPH winds (TX Hwy. 130 toll way), rain, dew, thermal cycles, etc. cause premature failure.

- Long duty cycles when dissipating up to 5.6 watts (28 VDC @ 0.2 amps) can over heat the relay solenoids in a confined space and/or when heated by direct sunlight on a warm (>100' F) Texas summer day.

- Shock and vibration when traveling on the highways and/or bumping down gravel roads

- Providing a reliable,  low RFI emission, source of 28 VDC power within a rover can be challenge.

- Yes, good low-loss and high-power coax relays aren't cheap (at least don't buy the cheap ones). As the length of your coax run increases the economics get better. My push-up mast extends up to 22 ft. (in order to get good 6 meter ground-bounce performance and raise my rover yagi stack over nearby obstructions, when necessary).

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Taming the Yaesu FT-857D for Rover Use

Repairing my FT-857D Transceiver

Sooner or later Murphy's going to get you! 
After using this rig for one contest (Jan. 2011) the maximum power output on 6 meters dropped to approx. 22 watts (100 watts normal) and peaks with an RF Power Setting of 40 (menu #75) using CW or FM modes. Grounding the "QRP" wire in the power cable reduces the CW or FM power output to 12 watts maximum. The AM maximum power is 12 watts (3 watts "QRP"). ALC indicates modulation on SSB.

Checking the other HF bands indicates that they are also running at reduced power however both the VHF (144 MHz) and UHF (432 MHz) power outputs are within specifications. All of the operating menu (and service menu) settings are normal. All power outputs were measured at 14 VDC with a Bird meter and 1:1 SWR dummy load.

So, it's off to find a repair shop. In the past I've used both the national Yaesu and local Burghardt repair shops. I'm sure that there are others out there:

• Yaesu Vertex Standard USA
• Burghardt Radio Repair

 Shipped to Burghardt on 5/26/11, stay tuned for the results! 
According to Jim (at Burghardt) the radio had suffered a high power spike; probably resulting from the close proximity of antennas while the yagi stack was "nested" (mast retracted). The 100W outputs from 2, 1.25 and/or 0.7 meters may have entered the radio via the 6 meter antenna causing extensive component damage. Note that the 70 cm per-amp located within the external amplifier was also blown!
Click here to read about my solution to this problem.

>>>Jan. 2013 Update: I used my repaired Yaesu FT-857D during the VHF contest. It performed flawlessly! I really like this rig for running the 4, limited-rover bands (50 - 432 MHz) with an external DEMI transverter for 222 MHz.  Of note are the DSP performance on both SSB and CW as well as the easy band and mode switching. I ran 6 meters with the internal 100W power output while using external 100W amplifiers on the 144 - 432 MHz bands. The "CW auto mode" (menu # 022) allows the CW key to be enabled even when you're in SSB mode.  This saves a lot of time when you need CW in a pinch!  Also note the full band-selected encoded BCD that's available on the CAT/Linear/Tuner output jack when "Linear mode" is selected (menu # 020).

My transceiver selection criteria consisted of:

1. Affordable
2. Remote control head
3. Built-in 100 watt amplifier on 6 meters
4. Adequate drive power for external amplifiers on 2 and 0.7 meters
5. Separate power output adjustment for each band
6. Controllable, low-level power 28 MHz IF for driving an external, 1.25 meter transverter (via ALC)
7. Ease of use and reasonable user interface
8. Highly effective noise limiter and IF DSP filters
9. Built-in CW keyer and memory keyer
10. Good sounding audio
11. Band-selected interface (for external band selected decoder)

I've used the Yaesu FT-847 for many years and was satisfied with it's operation so I went with the more compact and improved FT-857D.

FT-857D on-line references:

• Operating manual and download the pdf manual
• Service manual and download pdf manual
• KB2LJJ FT-857 Mods Database
• DXZone Ft-857 links

The ICOM 706MKIIG may also satisfy many of these criteria if this is your preference.

What I like least about the FT-857D:
I also discovered that the FT-857D had its share of "quirks" but most of these were overcome without too much difficulty:

1. DC current "spike" when the radio is first turned On.

2. RF power "spike" when PTT turns On (with lower power output levels) and limited delay (up to a max. of 40 ms) between PTT On and RF output. (Note RF spike of approx. 150% overshoot in screen captures below.)

20 ms delay (PTT-RF out) 1 Watt on 432 MHz

40 ms (PTT-RF out) 1 Watt on 432 MHz

 3. Minimum of 5 watts power output on all bands (unless you use the service menu settings or an external ALC voltage). 

4. Poor transceiver mode implementation (unusable in my case).


What I like most about the FT-857D:

1. Compact with remote head capability
2. Low noise cooling fan (when running)
3. Excellent noise limiter and DSP operation
4. Very quick to change modes, frequency and bands
5. CW AutoMode (menu#22) for automatic CW <=> SSB
6. Excellent audio with an external speaker (Cobra mdl. S300)

Mounting the remote, radio control head was accomplished using a 15" flexible gooseneck car mount kit from E-bay. It was easy to install with NO additional mounting holes required in my case.




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The DC Power Dilemma for Rovers

There are many trade-offs to be considered when it comes to supplying your DC power in a rover.










Ideally, the objectives are:

1. Voltage stability under maximum load current.
• In order to assure linearity of the amplifier RF output. I now run my DC bus at approx. 14.1 VDC (measured at the amplifier terminals under load).
2. Minimum voltage drop in the primary and secondary distribution cables.
• This may require short, higher gage cables and low voltage drop fusing.
3. Capable of handling worse case power duty-cycle.
• Battery capacity (Amp Hours) for transmissions during periods of high run-rates
• Recharge capacity to avoid battery low-voltage drop-out
• High charger and/or voltage booster efficiencies
• Real-time voltage and current monitoring
4. No noticeable RF noise emissions.
• Either radiated or conducted.
5. Safe operating, charging and off-line storage.
• Isolation from main vehicle battery, if connected
• Battery disconnect switch
• Protection from battery tip-over
• Protection from over charging
• Venting of gases from battery charging
• Proper grounding
• Proper fusing
• Proper fire extinguisher type and capacity
6. External Generator Safety (if used).
• Safe fuel storage
• Protection from hot surfaces
• Venting of noxious exhaust gases

After many years of trial and error I've arrived at some recommendations. Check them out and let me know about your experience and solutions. 

Click here for information regarding the Spectrum Control DC feed through EMI filters. I used the high DC current SCI 52-226-006 part number for both input and output connections.

It's also important to use a relatively short, heavy cable for DC power distribution between the voltage stabilizer and the load. I also use ferrite doughnuts to further surpress any conducted RFI.
Note that there's a remote voltage sense capability built into the voltage stabilizer that I haven't tried to use yet. There is also a remote monitor and On/Off interface. You must enable the On/Off control line (with + 12 VDC) to turn the voltage stabilizer On. However, if the voltage stabilizer is cool it won't start until it warms up by drawing current for a period of time. Then it's usually good-to-go for the rest of the day. I don't control the On/Off control line with PTT. Rather I leave it On (connected to + 12 VDC) for day.

The DC Power Stack

For lower current applications a TG Electronics boost regulator provides up to 40 A of regulated voltage at 14.5 VDC (adjustable). A boost regulator, PC Laptop power module and On/Off switch are shown mounted on top of a 12 volt marine battery case.









Click here for full screen view of the document.




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Rover (limited) in a rack (mini) project

Over the years I've enjoyed roving throughout the USA. With this project I hope to pass on some of what I've learned and encourage others. Much of this work is derived from other rovers who willing willing to share their experience with me.

The objectives of this project were to create a simple (KISS), replicate-able, low-cost, entry-level rover configuration to promote roving and lower the entry threshold for this experience. The "rover-in-a-rack" will be offered as a loaner station for locals who are interested in exploring this facet of ham radio (except when I'm testing it during the January contest in TX). So, if you you're qualified and have an interest in roving during the June, August or September VHF/UHF contests, please contact me for details. In any case, the information is available for anyone to use and improve upon. There are many good articles available on the Internet. I'll try to reference as many as I can find.

Vehicle modifications, antennas, masts, AC power, DC power, amplifiers, transverters and transceivers comprise the typical rover station. There is also much preparation required for a successful rove including route planning, publicity and bearing and distance calculating.

You're lucky if you have a rove buddy who can drive, navigate, operate, set-up and help keep the drive times more interesting. Consider this as a training position for future rovers.

Lastly, safe roving involves paying attention to driving while in-motion, properly installing your equipment and avoiding power lines and dangerous locations. Please be careful!

I'd welcome your comments to this blog and/or Email to k0mhc@arrl.net

73, Jim
KØMHC/Rover.
Kerrville, TX

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Smartphone Apps for Roving

I've used several apps for my iPhone that have been very handy during a rove. Here's a brief description and my usage notes:

Maidenhead Converter By Donald Hays

This app allows you to find your Maidenhead grid square identifier with up to 8 digit accuracy.

- 4 digits for general information exchanges

- 6 digits for UHF/microwave beam pointing

- 8 digits for finding the location again

It also allows you to convert back to latitude and longitude coordinates at a later date.




Just drive along with this display on your dash and you'll know when you're about to cross into the next grid at a glance. This app uses the internal GPS and no cellular/Internet connection is required.

Maidenhead by MacCon

This app is very handy for calculating bearing and distance between your rover and any other station by just entering their 6 digit Maidenhead identifier. It also provides a map view of your two locations. Your rover location is always updated automatically.

You can also set a mode whereby the bearing and distance between a fixed station (a big gun) and your rover is ALWAYS shown on the display. In this example, you never enter any new data as you roam around the countryside.

This app uses the internal GPS and no cellular/Internet connection is required.





Spyglass by Pavel Ahafonau

There are many uses for this very good compass app but, the one I use the most is to just calibrate my beam heading after stopping at an operating site. Yes, I need to study the quick start guide to see what else I can't do without!

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