VR N7500 Unhappy in Go Box

[Jeffrey Fritz]

I thought that my VR N7500 would make a terrific go box radio. It's headless, compact and relatively light weight. Plus I could use an Android tablet or the VGC BMH78 Bluetooth microphone to control the VR N7500.

I found that, while the VR-N7500 works great in my go box when connected to either one of my outside mounted verticals, it goes bonkers when it is attached to a go box mounted antenna. It will sometimes transmit properly, but often all three LEDs (orange, green and red) will come on and the rig will either shut off momentarily or shift to another channel.

At first I thought that I might have a VSWR issue, but checking this I found that the VSWR on either go box mounted antenna (a Comet B-10 or a Diamond SRJ77CA) was always 2.5:1 or less at the rig.

I tried using another rig in the go box (a Yaesu FT-2980) and it worked perfectly. This suggests that the VR-N7500 (or at least my unit) does not like having an antenna that is in close proximity to the rig. 

I would accept this as an explanation except that I know that some of you are using this same rig with your motorcycles. I can't imagine that there is all that much distance in your case between the rig and the antenna, So I remain mystified.

I'd love to hear from anyone who has successfully used the VRT-N7500 in a go box.

73,

Jeff, WB1AAL

[johnny keeton]

Jeff, 

Do you have pictures of how it is hooked up? I use mine with my go kit and an arrow dual band antenna all the time. No issues.

Johnny (KJ7DAK)

Sent from Yahoo Mail on Android

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[Marnoch Standen]

Hi Jeff and Johnny

 

I believe you RF getting into the radio and bonding of radio to box would be essential plus such a small ground plane there is going to be some high SWR that your seeing. This means the radio is seeing high return power. Other radios may have a network circuit that will reduce TX power thus allowing it to operate (save the final PA) and I’m not sure if this feature is in the VR-N7500 .

 

On the bike mine is sat in plastic biscuit container  inside the top box with the antenna fixed to the top or side of the top box. I have never seen any issues and used different antenna till I found a suitable one.

 

You are in the correct direction, removing the high SWR by some throw out ground planes, turn the SWR down by bending the wire back.

 

Let us know how you get on ..

 

Min G0JMS

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[Jeffrey Fritz]

I very much appreciate the help that I received from Min and Johnny on my go box issue.

I have found that my particular VR-N7500 is very susceptible to RFI. Even using an external mag mount antenna with the go box, the radio has issues. The VR-N7500 sometimes shuts off momentarily and the receive becomes intermittent. This caused great confusion on a two-meter net the other night when I was unaware that other stations were transmitting. 

This is an issue whether or not the aluminum frame is grounded to the antenna ground, whether or not the radio is bonded to the ground and regardless of what mobile antenna is used. 

There is, of course, a metal case shielding most of the radio,  However, the front panel is not metal and therefore unshielded from RFI. My external Bluetooth antenna modification may not be helping either with preventing RFI.

The radio works very well as a base station when connected to the vertical mounted on my roof. It has no RFI issues whatsoever, so that’s the way that I will use it. I have ordered another dual band transceiver to use in the go box. 

Thanks again for all the help!

73,

Jeff, WB1AAL

[Marnoch Standen]

Hi Jeff

 

Thought on last email.

 

Supply to radio Battery or Mains  - If battery is it sagging below the design operating voltage 12.5 volts to give you a guide.

It sounds like the radio is rebooting causes are power or RF getting to it via power leads or RF feedback. But rebooting sounds like lack of voltage.

What TX power are you using?

 

My motorcycle top box has the antenna on top of it and the radio sat inside doing RF APRS and coms.

 

Strange issue and hope you let us know if you sort it.

 

Min G0JMS

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[Jeffrey Fritz]

Min,

This issue occurs whether I use a battery supply or an AC mains power supply. And it can happen at high or low power. It is frequency dependent suggesting that this is indeed RF getting back into the radio. 

I have ordered another radio (a Retevis RT-95 to use in the go box and have placed the VR-N7500 back on the outside vertical. I will continue to use it as a base station radio as it works just fine on the outside antenna. 

73,

Jeff

[Marnoch Standen]

Good luck with this as it seems strange it must be RF getting into the radio and I wonder if putting RF filter choke on the DC power lead would help. 

You may have tried it already.  

We will sort this out.  

Min Standen G0JMS

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[David S]

Quick question Jeff, 1/4 wave or 1/2 antenna?

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Thanks, David

KE6UPI

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[Jeffrey Fritz]

David,

I’ve used both a 1/4 and 5/8 wave (at two meters) antennas with the radio. Both have been used with and without a ground plane. The result was the same.