Antenna Dilemma

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gigyahurts

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I have an 80M loop and a tri band (Diamond V2000) antenna. I want to share them with a TS2000 and an AR5000. I can insert a solenoid operated antenna switch like this (RF Parts Company ~ CX-800M Specs) to isolate the AR5000 when transmitting but will lose the TS2K as a receiver. I can place a splitter in and then the switch if it will handle the transmit power but with reduced frequencies and losses.

Is there any kind of splitter that will allow receive on both radios without huge losses and is suitable for transmitting? Any other solutions I am missing? Thanks.
 

n9mxq

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The problem with that, if I understand your intentions, is that when you transmit with one, the front end of the other will be overloaded, and most likely, damaged.
 

gigyahurts

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That is where the solenoid antenna switch comes in. When the mic is keyed, the antenna switch opens up the receiver antennas and closes the transmitter antennas.The positive to this mode is the radios have no real losses from a splitter but if the plug in the back gets disconnected, it could transmit into no antenna. Also, the transmitter is not able to receive.

If I add a splitter that can handle 100 watts ahead of the antenna switch, the transmitter is always connected and can receive at all times while the receiver is disconnected when the mic is keyed. The negative about this is that I can't find a splitter that will handle the 100 watts out and the loss of 3.2 to 4.6 db from the splitter. http://www.minicircuits.com/pdfs/ZMSC-2-2.pdf http://www.minicircuits.com/pdfs/ZAPD-30+.pdf

Any ideas?
 

n9mxq

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So, if I'm following this right, you'll have both rigs connected to the solenoid switch, which in turn will be connected to the 2 antennas via an antenna switch?

RIG1--------\ 80Meter Loop
Solenoid switch---Coax Switch---<
RIG2--------/ TriBander

Right?? I'm not seeing where a splitter would go....Maybe I'm confused....
 

LtDoc

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Maybe you could explain your point with this, what you hope to accomplish? I'm not following it at all.
- 'Doc
 

gigyahurts

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Asci art never works for me either! :)

What I would like to accomplish is to receive off both receivers at the same time from either antenna and occasionally transmit on the transmitter without blowing out the front end of the receiver. Both rigs need both antennas to receive. I would like this to be effective, simple and inexpensive but I would consider it a bonus if I got more than one of the three accomplished.

Each antenna coax would go to separate splitters. Then both coaxes from side "a" of the splitters would go to the transmitter and side "b" of the splitters would go to the dpdt antenna switch NC side which would then go to the receiver. When the mic is keyed, the switch would open both antenna coax feeds to isolate the receiver front end.

I am sure other people must have hit this problem before and I hope there is a better way than what I just described.
 

Token

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To your basic question of is there any kind of splitter that will allow both to work without large losses the answer is no, there is not. A splitter is dividing power, particularly on transmit this is going to be very noticeable, losses will not be "larger" on transmit than receive, but transmit is where it will likely be most apparent.

The TS2k has separate antenna jacks on the back panel for each band, HF/6M, 2M, and 70cm. As the V2000 is a single feed 6M/2M/70cm antenna I assume you are doing something like assigning HF below 6M to HF Ant 1 jack and 6M to HF Ant 2 jack, and then using say a "triplexer" to combine the HF Ant 2 jack, 2M jack, and 70 cm jack into a single feedline to go to the V2000. Then the HF antenna (80M loop) is connected directly to HF Ant 1 jack.

In addition you want the AR5000 to be able to use the same two antennas for receive, having the TS2k and AR5000 in parallel on both antennas for receive purposes and muting and the AR5000 (and switching away the antenna) during TS2k transmit. Since the AR5000 also has 2 antenna ports you will not have to combine the 80M loop and the V2000 feedline for the use of the AR5000.

The power divider on each of the two antenna feeds that allows both the TS2k and the AR5000 is going to exhibit at least 3 dB of loss for each radio, at best (this means your 100 Watt TS2k just became a 50 Watt radio, at best, and probably more like 35 Watts). And to tell the truth I am not really sure one exist off-the-shelf that will work at the power levels you want, and if it does exist it will probably be a commercial unit, with the associated cost. The reason one might not exist is probably because this is not a very good idea from an equipment life standpoint. And the coax switch you point out probably does not have enough isolation by itself, you might want to add a second coax switch in each line that takes the AR5000 input to ground when the TS2k transmits. The spec sheet says 50 dB isolation in HF and less than that in VHF/UHF, that means that your 100 Watt TS2k (+50 dBm) will be whacking the front end of your AR 5000 with say +0 to +13 dBm, or more than 130 dB above its noise floor, if the switch is working at its best, and I have often found those kinds of switches to decrease in isolation over time. A honking big signal for the AR5000, maybe not enough to hurt it, but I would not be too sure.

It is mostly a poor practice to have wideband receive equipment attached to the same feedline as transmit equipment, particularly with only an antenna switch before the RX equipment and not some kind of sequencer and additional RX protection. Yes, I know that separate receivers and transmitters on a single feedline/antenna were common in the earlier days of amateur radio, I did it often myself. But the probability of a failure or incorrect switch setting with what you are describing is fairly high, and I can almost guarantee you transmitting 100 Watts out of the TS2k into the front end of the AR5000 one time by accident will cause problems.

What you want to achieve could be done, but you might have to build a few pieces/parts yourself to do it. Personally I would not try to make this happen. I would use separate antennas for the TS2k and the AR5000, and I still might (depending on how much and what kind of antenna separation you can achieve) include antenna switching in front of the AR5000 to kill the RX when the TS2k was transmitting.

There is certainly no off-the-shelf answer that I have seen recently that will be effective, simple, inexpensive, and dependable.

T!
 

gigyahurts

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Thank you very much for the detailed response, Token! All your assumptions are spot on as to my current antenna layout. I am rather new to radios and at the low end of knowledge in electronics so I really appreciate the help.

So two new antennas it is. With separate receive only antennas for the ar5k, the dpdt switch should be ok to isolate both receive coax's when the transmitter is running. I can further ground the NO side so that nothing goes into the ar5k when the transmitter is running.

I was thinking about putting up a larger loop anyway. If it is a receive only loop, what size would you recommend? If I made it 160 I would have the option of manually connecting it to the transmitter on the rare times I need the longer band.
 

Token

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Thank you very much for the detailed response, Token! All your assumptions are spot on as to my current antenna layout. I am rather new to radios and at the low end of knowledge in electronics so I really appreciate the help.

So two new antennas it is. With separate receive only antennas for the ar5k, the dpdt switch should be ok to isolate both receive coax's when the transmitter is running. I can further ground the NO side so that nothing goes into the ar5k when the transmitter is running.

I was thinking about putting up a larger loop anyway. If it is a receive only loop, what size would you recommend? If I made it 160 I would have the option of manually connecting it to the transmitter on the rare times I need the longer band.
With separate RX antennas and a little separation (vertical separation on the VHF/UHF side works well, say the AR5k VHF/UHF RX only antenna mounted below the TX/RX V2000 if that is possible with your installation) you probably do not need the coax switches at all, but they would be extra insurance and would not hurt to have. For one of my VHF/UHF scanner antennas I use a discone mounted on the same tower but 10 feet below a Diamond F23H 2M antenna, I desens the scanner (Icom R8500) a bit when I TX on 2M, but it is not bad at all. With 20+ feet of horizontal separation you could add 60+ dB of isolation to the 50 dB of the coax switch, depending on frequencies, antennas, etc. There are WAY many variables here so hard to talk in more than generalities without specific details.

I have used a 160M full wave skyloop as an RX antenna before. Results were generally good but trailed off at upper HF frequencies. I would say excellent to about 12000 kHz or so, and noticeably falling off above that. And yeah, is nice to have it for when you want to TX on 160 also. However, my favorite general purpose RX antenna for HF right now is a three band single feed inverted V. Kind of like a fan dipole/in-V but not quite. I really did not put the feed point up high enough at 160M to call it a true inv-V antenna, more of a dipole with the ends lower than the feed, this was done on purpose to take advantage of the off the end directional cone at higher frequencies. It is high enough to act as an inv-V at 80 and 60.

I built it for three bands, 160M, 80M, and 60M. I then ran the three band legs in different directions, in my case the 160M runs from 290/100, the 80M runs 350/170, and the 60M runs 040/220. Between the bands and the harmonics/multiples that these three antennas hit it works pretty well (RX only or with a tuner on TX) all the way up to 30 MHz. One thing to remember is that a wire antenna, inv-V, dipole, long wire, anything, is going to start showing directionality towards the ends (not the side) as frequency increases and wavelength of the wire at the given frequency increases. The higher the frequency, and longer in wavelength the wire, the more towards the end it will be. So that for practical purposes you can view a 160M inv-V or dipole as having 4 main lobes at frequencies above say 12000 kHz. I positioned the antenna to roughly point the cones off the ends in desired directions.

Lots of options if you have a little bit of room to play with, and wire is relativley cheap to experiment with.

T!
 

gigyahurts

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Once again, thanks for the detailed info! I will start off with my constraints.

I have no tower and no plans of installing one as I am shooting for a low profile installation. The geography is very hilly. The house sits on a east west ridge with sloping down ground from appx 160 to 30 deg clockwise and a large steep slope upwards appx 100m east and 30 m high which is a north south ridge. There are two feed points, one about 25m east of the house which runs underground in a very small conduit (I made the huge mistake of thinking I would only ever need one antenna!) and one that comes from my chimny to the wall penetration. I could bring the other two feeds in here. The chimny structure provides for a place to tie off wire antennas and mount the vhf antenna. The ridge acts as another convenient point to tie off wires and provides 10 to 12 m of elevation for the antenna after sag. There are no trees higher than the house except on the ridge which makes the multidirectional antenna problematic without a tower.

After thinking about your 160-80-60 antenna it makes a lot of sense with a minimum selection of wires whose multiples will fill in the spectrum. I have a huge hole in the 60m area with my current antenna where it is well over 10:1 swr. Initially I will run the loop as I can do it very easily in a triangle config (two points on the ridge and the chimny) while I think of methods to implement the multiwire. The losses above 12mHz concern me though.

The orientation of the two antennas would be with the new 160 as a horizontal loop running from the chimny to the ridge bearing 120, to the north part of the ridge at 0 and then to the chimny bearing 210. The existing antenna is a 80 superloop vertical with the aperature facing north south and the support wires running east west. This antenna will set inside the perimeter of the new 160 horizontal loop.

The new discone antenna (Diamond® Antenna ~ D3000N Super Discone Antenna opinion?) can mount to the other side of the chimny but will be level and only a meter away or I could mount it lower on the roof somewhere but would lose some height and los due to the roof obstruction.
 
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