31-08-2017, 08:14 AM
John
We have been away in the van a couple of times since that write-up, the most recent with us arriving back at home yesterday, and each time I have tried something different with antennas etc.
This last effort was comparing the wire up the middle of the 7M squid pole to a 19 metre length of hookup wire stretched out longwire-style up into a tree. Just perchance (or not), that wire length resonates on 80 metres... I tried two different styles of UN-UN with them and came to the conclusion that the 4:1 version works well for 10MHz and up with the squid pole but a straight multitapped toroidal single-winding inductor works better for 7 and 3.5 MHz, longwire or squid pole, and connected to the highest impedance transformation point. The 'ground' side of the UN-UN was clipped to the chassis on the caravan drawbar. I will probably make up a 9:1 or 16:1 conventional UN-UN (or both) to try out on our next outing, with the same two antennas.
The variation in propagation over a fixed length path even just on 40 during the afternoon is something to behold. Similarly, prop on 80 is variable but probably not as noticeable. It would have been good to have be able to try again on 5MHz as a rough frequency mid-point.
I didn't put photos of inside the van in my write-up but, verbally, a foam-RG58 coax from both front and back mounts travel under the van floor and up and into a cupboard then behind the air conditioner and pass through the top A/C cupboard vent and are terminated in BNCs and coiled up on the top of the cupboard. They have company in the form of two RG6 coaxes that are terminated in F sockets mounted under the van and the top ends are again F's and coiled on the cupboard top. There is a 4-outlet AC power board up there too so that either the transceiver's 240VAC power supply can be connected and/or the satellite TV box powered. I have a a heavy duty 50A anderson style socket, fused for 40A, handy to the van battery to allow for 12VDC operation, plus an anderson-to-anderson extension power lead made from a 100A car jumper lead set plus a couple of 1.5 metre long BNC-BNC leads, all making radio positioning simple and flexible.
There are always ways to do the physical positioning within the van but getting approval from the "boss" is not always so simple. I usually opt for the 'forgiveness procedure' - install it first then seek forgiveness afterward saying 'it's all finished now'....
73 Doug VK4ADC
We have been away in the van a couple of times since that write-up, the most recent with us arriving back at home yesterday, and each time I have tried something different with antennas etc.
This last effort was comparing the wire up the middle of the 7M squid pole to a 19 metre length of hookup wire stretched out longwire-style up into a tree. Just perchance (or not), that wire length resonates on 80 metres... I tried two different styles of UN-UN with them and came to the conclusion that the 4:1 version works well for 10MHz and up with the squid pole but a straight multitapped toroidal single-winding inductor works better for 7 and 3.5 MHz, longwire or squid pole, and connected to the highest impedance transformation point. The 'ground' side of the UN-UN was clipped to the chassis on the caravan drawbar. I will probably make up a 9:1 or 16:1 conventional UN-UN (or both) to try out on our next outing, with the same two antennas.
The variation in propagation over a fixed length path even just on 40 during the afternoon is something to behold. Similarly, prop on 80 is variable but probably not as noticeable. It would have been good to have be able to try again on 5MHz as a rough frequency mid-point.
I didn't put photos of inside the van in my write-up but, verbally, a foam-RG58 coax from both front and back mounts travel under the van floor and up and into a cupboard then behind the air conditioner and pass through the top A/C cupboard vent and are terminated in BNCs and coiled up on the top of the cupboard. They have company in the form of two RG6 coaxes that are terminated in F sockets mounted under the van and the top ends are again F's and coiled on the cupboard top. There is a 4-outlet AC power board up there too so that either the transceiver's 240VAC power supply can be connected and/or the satellite TV box powered. I have a a heavy duty 50A anderson style socket, fused for 40A, handy to the van battery to allow for 12VDC operation, plus an anderson-to-anderson extension power lead made from a 100A car jumper lead set plus a couple of 1.5 metre long BNC-BNC leads, all making radio positioning simple and flexible.
There are always ways to do the physical positioning within the van but getting approval from the "boss" is not always so simple. I usually opt for the 'forgiveness procedure' - install it first then seek forgiveness afterward saying 'it's all finished now'....
73 Doug VK4ADC
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.