GME 300 Questions

[esajoda]

Hi,

To all the people with the answers.

I have a questions, on a recent trip I picked up the following observation, when the distance between the vehicles increased (+/- 4kms) my radio(GME300) was able to still receive the conversation from the other vehicle but they could no longer hear me.
Why did this happen?

Jose

[CasKru]

You will always here further than you speak, unless you find a skip where the signal gets amplified somehow to reach you. I once when I was still at tech, spoke to someone in some island group sitting on his yacht using my 29Mhz.

[Mud Dog]

When conditions are right, the signal can bounce off the ionisphere creating a 'skip'. Occurs very occasionally that there is someone on the same frequency in the right area.
Perhaps Eric can confirm / elaborate.

[Family_Dog]

The biggest influence on RF transmission range is always the antenna, and the position in which it is mounted. The most ideal spot is slap bang in the middle of the roof, where it can use the metallic roof surface to provide a ground plane in all directions, resulting in an ideal radiation pattern. But this is not always possible nor practical, so we usually mount it on the B or C pillar of the vehicle, as high up as possible in order that the radiating part of the antenna, i.e. the whip, is not blocked by any metal surface. This compromises matters somewhat but works well enough for most of us.

Many of us, myself included as far as Bulldog is concerned, have mounted the antenna on the Bulll Bar, which is totally unsuitable for a low-frequency radio such as a 29MHz of any sort. This really distorts the radiation properties of the antenna and the radiation path becomes very directional and in fact very poor forward of the vehicle. But as I am quite content with only 3-4kms range in any case, I live with the convenience that the Bull Bar mount provides.

During tests that we conducted between the Dragon and the GX300, we found that the Dragon has a slight advantage in Transmit power ( around 10-20%) over the GX300 (see last paragraph hereunder), but the GX300 has a far superior receiver than the Dragon. Your experience confirms this: You are able to receive better than you can transmit. But the small power difference in Transmit, although measurable on sensitive instruments, will never provide any meaningful difference over transmission paths at all, you would require about 300-500% increase in Transmit power before you could even imagine that you hear any difference. The more sensitive and selective receiver, on the other hand, makes a huge difference, equating to the remote transmitter having a signal strength up to four times stronger than it really is.

Be that as it may, the GX300 has been unavailable from Avnic for nearly three months and the new stocks arrived only this week. They are reported to have "enhanced broadcast and audio" capabilities. I have received my new stock but have not yet conducted any further tests on the units.

There is always the possibility of "skip" distances being obtained with a 29MHz radio, caused by the radiated RF bouncing up and down between the ionosphere, as Cassie & Andy mentioned. But in general, we are more concerned with the 'ground-wave option', i.e. how far we can communicate at all times.


-F_D