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  #1 (permalink)  
Old 10-07-2018, 9:01 AM
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Default Switch from mobile CB install to Ham 2m/70cm

Hi everyone,

I currently have a CB hardwired to my car and Iíve got a Larsen NMO-27 mounted to my roof via an NMO mount. As many of you know CB is all but dead anywhere I go, and Iíve been thinking about redoing my set up with a Lexien VV-898 instead of the CB, but I have a few questions. I do not have my Technicianís class license yet, but I am studying for it and taking practice tests online.

The CB Iím using is a basic Uniden 510 with no mods. I have a 98 Volvo V series car, and Volvos from that era have a fused accessory port which the Uniden is hard wired into on a 30 amp fused, constant hot connection. If I got a VV-898 or similar small 2m/70cm Mobile radio, would this power connection still be ok, or would I need to run the power wire directly to the carís battery?

As far as the antenna, I have the NMO mount dead center in the steel roof of my car (no sunroof), which is ideal for CB. I have a 3Ē spring between the base and the whip, and I have a home-made wooden dowel attached to my rear roof rack with holds the whip down when not in use so I can park it in my garage. Iíve got a top quality shielded NMO mount and I used the best quality coax I could get to go from the NMO to the CB, which is about 8í away. Since my cable is 12í , I do have it in a big loop up in the headliner before it goes down the passenger side pillar and to the CB which is mounted under the glove compartment. I know I will need to get a new antenna to go with the new radio, but will those extra loops of wire in my line be a bad thing for HAM signals? Again, I donít have my Tech class license yet, so Iím not 100% sure this CB-based setup will need to be modified or not.

My last question involves grounding for the antenna. I am considering putting an all-metal Redline trailer vent in the roof of my car where the sunroof would be. This is sort of like the metal vents on the side of Grumman step vans or LLV US Postal trucks, but they are about 2Ē high and meant to be installed on a roof, not on the side of a trailer. Anyway, they are all metal, including the internal lever which allows the vent to pop up. If I install this vent, there will be a gasket between the vent and the roof, but Iím concerned about getting shocked if the radio was transmitting and someone was touching the metal lever in the vent.

Well, before I buy any new equipment or install anything else in my roof, I wanted to get these questions out there. Any feedback you could offer would be a big help, thanks.
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Old 10-07-2018, 9:45 AM
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I own a VV898 and the current draw on "full power" transmit is well under 30 amps (more like 3 amps), so your current wiring should be a non-issue.

As for the antenna, since the VV898 is dual-band, you will need a dual-band antenna. Although others will argue against a "hammy antenna", I would suggest one of these:
https://www.gigaparts.com/diamond-an...ontent=Diamond

The problem of someone getting "shocked" from touching the roof vent lever is a non-starter. There is zero chance for that since the transmitted power is way too low for that to become an issue.
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Old 10-09-2018, 3:19 PM
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Use the power formula P = IA. The power draw for the VV898 would be 10 watt (actually a bit more to control the display and various other internal workings) divided by 12.5V (as high as 13.8V) and you're at under 2 amps.

William has personal experience with the same radio, so I'd believe his number.

Is the current radio wiring tapped into a true 30 amp circuit, "down stream" of the 30 amp fuse, or is it tapped on the battery side of said fuse? It makes a difference. Option one at least has some protection, but option two has no protection other than any fuse you installed yourself. On a CB, since you're limited to about 4 watt, anything over 5 amps is over kill.

If you are never going back to a CB, you could manually cut your antenna down to be a decent dual band. But you'd want to try with a random stick of metal to practice.

As long as the vent is not touching any part of the antenna whip, you're going to be fine. And as William pointed out, it won't be a problem anyway. If the vent is screwed to the roof, it will make some electrical / RF connection to the roof.
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Old 10-10-2018, 11:32 AM
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I think you will be fine on the power set up. It's possible you'll get some electrical noise on the new radio, but there's no way to predict it and you can deal with it when (or if).

You made a wise choice going with an NMO mount! I'd recommend the Larsen NMO 2/70 antenna. There's also a shorter version if you are worried about antenna length.
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Old 10-10-2018, 12:46 PM
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Sonic...I just left the leixen website and noticed that the vv898 is listed as discontinued for $45. Beware of radios that are being discontinued (esp. Chinese radios) because that neans little to no support from the company. I personally would not go with a Chinese radio but would go with a better build radio. You can get a name brand single band fsor the price of a cb and a dual band cheaper than a ssb cb. Remember you usually get what you pay for....a $45 radio is still a $45 radio. The rest of the setup that you described will work ok. Just replace the antenna witha 144/440 antenna and you will be ready to go. Good luck on getting your license.
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Old 10-10-2018, 1:56 PM
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Sonic, Good luck on your test.
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Old 10-11-2018, 10:30 PM
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Quote:
Originally Posted by KD5TMS View Post
Use the power formula P = IA. The power draw for the VV898 would be 10 watt (actually a bit more to control the display and various other internal workings) divided by 12.5V (as high as 13.8V) and you're at under 2 amps.

William has personal experience with the same radio, so I'd believe his number.

Is the current radio wiring tapped into a true 30 amp circuit, "down stream" of the 30 amp fuse, or is it tapped on the battery side of said fuse? It makes a difference. Option one at least has some protection, but option two has no protection other than any fuse you installed yourself. On a CB, since you're limited to about 4 watt, anything over 5 amps is over kill.

If you are never going back to a CB, you could manually cut your antenna down to be a decent dual band. But you'd want to try with a random stick of metal to practice.

As long as the vent is not touching any part of the antenna whip, you're going to be fine. And as William pointed out, it won't be a problem anyway. If the vent is screwed to the roof, it will make some electrical / RF connection to the roof.
So, Volvo has an accessory plug that is up on the driver side firewall. It has a total of six different connections, each with different options for constant hot, ACC II On, etc. There is a special fuse pane for this accessory plug, so I am wiring to a soldered connection at the plug, which is then fused up in the main fuse box. Iím not just tapping into the hot side of a fuse, and Iím not running the wire directly to the battery. For the ground, I have a short wire from the CB with a lug soldered to the end and itís bolted to the frame of the passenger door jamb up under the dashboard. Iíve not had any issues with the power supply since wiring this all up.

For the antenna, Iím hesitant to cut it as I might sell it, but Iím open to it if it would save me money. Wouldnít the size of the base load on a Larsen 27 be wrong for 2m/70c?
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Old 10-11-2018, 10:34 PM
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Quote:
Originally Posted by sloop View Post
Sonic...I just left the leixen website and noticed that the vv898 is listed as discontinued for $45. Beware of radios that are being discontinued (esp. Chinese radios) because that neans little to no support from the company. I personally would not go with a Chinese radio but would go with a better build radio. You can get a name brand single band fsor the price of a cb and a dual band cheaper than a ssb cb. Remember you usually get what you pay for....a $45 radio is still a $45 radio. The rest of the setup that you described will work ok. Just replace the antenna witha 144/440 antenna and you will be ready to go. Good luck on getting your license.
Thatís interesting. They seem to be readily available everywhere and get good reviews. Are they replacing it with something?

Iím not opposed to spending twice that for a good radio, but do you have any recommendations? I need something small, as my Uniden 510 fits perfect in the opening Iím using and the Lexien would fit even better because while slightly taller, itís much less deep than the 510.

I donít really want to spend $300, although I know there are good ones out there. It seems like there is no middle ground radios - itís either CCRs for less than $100 or Yaesus for $250+.
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Old 10-12-2018, 6:40 AM
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Quote:
Originally Posted by KD5TMS View Post
Use the power formula P = IA. The power draw for the VV898 would be 10 watt (actually a bit more to control the display and various other internal workings) divided by 12.5V (as high as 13.8V) and you're at under 2 amps.

William has personal experience with the same radio, so I'd believe his number.

Is the current radio wiring tapped into a true 30 amp circuit, "down stream" of the 30 amp fuse, or is it tapped on the battery side of said fuse? It makes a difference. Option one at least has some protection, but option two has no protection other than any fuse you installed yourself. On a CB, since you're limited to about 4 watt, anything over 5 amps is over kill.

If you are never going back to a CB, you could manually cut your antenna down to be a decent dual band. But you'd want to try with a random stick of metal to practice.

As long as the vent is not touching any part of the antenna whip, you're going to be fine. And as William pointed out, it won't be a problem anyway. If the vent is screwed to the roof, it will make some electrical / RF connection to the roof.
RF output does not equal the transmit load. Remember conservation of energy, Ein equals Eout which can be rearranged to Pin equals Pout. Most FM transmitters are about 25% efficient (meaning for every 100W of draw, 25W of RF and 75W of heat) but that's an average from multiple radios over the last few decades (18% for Motorola's LPI GM300's of the early 90s, 34% for Yaesu's current single band 2m rigs).

Point being, a 10W radio presents something more like a 40W load when transmitting. 40W breaks down to about 2.9 A at 13.8V.
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Old 10-12-2018, 7:07 AM
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Default VV-898 install

Having 2 of these radios from different Chinese vendors I can say that you cannot go wrong and get a "dud" Having also said that, different chinese vendors may be less than throwing your money away. Leixen is not going out of business they will be around perhaps under a different name as is the case with many vendors both here and overseas.

The VV-898 is perfect for small cars or even a motorcycle so space wise its a "fit". Your going to pay for a decent dual band antenna though with most being in 25.00 range for what you need. If UHF is never to be used on your part, go with a mono-band 2 meter mobile antenna and your done except for the mounting part.
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