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Thread: Wideband Low Band antenna ideas Syntor X Low Band

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    Default Wideband Low Band antenna ideas Syntor X Low Band

    Looking at adding low band to my mobile capabilities. I have my eyes out for a Syntor X so I can have 10M and 6M capabilities. Yes, I can cobble up two antennas and a tuned coax harness to get the two ham bands, but I want the itinerant Part 90 channels in between. Repeater-Builder hints at using a screwdriver antenna or an SGC tuner, but offers no practical solutions.

    Here are my ideas;

    A screwdriver type antenna with a JT Comm Tunematic automatic tuner (Motor controller)

    A whip with an SGC type PI/LC tuner. The problem with these are that they are very limited to CW power, especially the ones that cover 6 meter (60 MHz models). A Syntor X LB will do 108 Watts easily. Some of the SGC models need a 40 foot radiator.

    Any ideas how to maximize this mobile installation?

    Can an automatic PI type tuner load an antenna less than 9 feet? In other words, could a base loaded 4 foot Larsen antenna be fed by a tuner?

    What are the MIlcom folks doing? No I don't want a whip from a tank..


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    I’ve got syntor X’s in the 30-50mhz flavor. PM me if you’re interested.

    Seth

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    I don't think there are any license free B/ILT itinerants on lowband...

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    Quote Originally Posted by d119 View Post
    I don't think there are any license free B/ILT itinerants on lowband...
    True but it is very easy to obtain a part 90 license if you have a business which I do.

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    Where are the antenna experts?

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    I believe Motorola sells/recommends a screwdriver-type of antenna for the Lowband Syntor-X/X-9000 radios, AFAIK. I'm not sure what the model/part # is, but I do remember that was their solution.

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    This is expressly what you don't want, but this is what I use;
    AS-3900A/VRC
    https://www.rami.com/product/as-3900avrc/

    Covers the whole band, poorly, but does

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    Armoured vehicle antennas for this band are typically a centre fed sleeve dipole. They radiate reasonably well but the VSWR is high at the band edges. The match can be improved by a tuner but that doesn't alter the antenna performance.

    The screwdriver is a logical choice, full 1/4 wave over the band but you will either need to use a manual controller or find an auto controller that works over the whole 30 to 50 MHz range. You may also need to modify the Syntor to allow an external tuner control line to select low power as some tuners require low RF power during tune. Another issue with the screwdriver is grounding, on HF it doesn't matter much if the base of the antenna is a foot or so away from the vehicle body as long as a good ground strap is used, but at 6m a foot of ground cable will mess up performance.

    One idea I've not tried is a glorified donkey d!ck made of PVC or fibreglass tube, say 1 to 2" diameter, with three or four wire or alarm foil tape parallel radiators each cut for a particular frequency. Each would be open at the top but joined at the base. While not totally agile, you might be able to support 10 and 6m plus a couple of commercial channels. Rather like half of the popular multiband band parallel wire dipole design.

    Lastly, a single 55 MHz quarter wave with a custom tuner. This whip will need a motorised roller inductor at the base to bring it to resonance as it's shorter than a quarter wave at all your frequencies. This will not be as efficient as a screwdriver but could be much lower profile. You could for example mount the whip on the centre of the trunk with the tuning assembly mounted on the underside of the trunk lid.
    It is a fine thing to be honest, but it is also very important to be right

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    While the Syntor is the go to Moto option, don't overlook the TK6110. I have a coupe of these broadbanded for 29 to 53 MHz and they work rather well at 50W.
    It is a fine thing to be honest, but it is also very important to be right

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    Some good ideas there. I like the multi filar DD idea. The 100 watt, 6 meter requirement indeed has limited the number of automatic tuners available to tune a fixed whip. The screwdriver and autotuner idea also has only a limited number of products and high cost per my initial research. Most products are for 100 to 150 W SSB. 100 W FM has a potential of damaging relays and roller contacts.

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    Quote Originally Posted by Astro Spectra View Post
    While the Syntor is the go to Moto option, don't overlook the TK6110. I have a coupe of these broadbanded for 29 to 53 MHz and they work rather well at 50W.
    I love my 6110. I got one a few years back after hearing they can be brought to the 6 and 10 meter bands easily. I never got around to it as its still in commercial service. I like how it can scan the full 32 channel capacity. Just about the only improvement I wish I could make would be to increase the channel capacity.

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    Just grabbed a few Syntor X9000s to do the 128 channel codeplug push to... and would love to figure out a "decent" antenna that won't break the bank. The military center-fed dipole is probably the cheapest of the bunch - but I have no idea how the radio will behave with that much of an SWR on the band edges... especially down around the 10m area.

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    If you only need to transmit on 10 and 6 two antennas with a critical length coupling harness works just fine. I ran that setup on my old Tahoe. RX across the entire low band range is excellent.

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    In my case, I would like to include some part 90 freqs Midband , so a 10M, 6M fix is not enough. I am surprised Motorola would develop such a radio without a wideband antenna solution,

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    Luckily one of these will be a base install... so I guess a few antennas and a coax switch can be a sorta-solution. But I agree - a wideband solution would be nice.

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    Maybe use a 10 meter antenna fed into an sgc auto tuner? SG-237 covers up to 60 mhz at 100 watts.