Simplex, antenna choice and signal strength required?

[N2MRG]

I have been trying to run some numbers into Radio Mobile to see if my wife and I would be able to talk about town from a mobile to a base station at home via simplex. There is no GMRS repeater around and my wife is not licensed on amateur (doesn't want to either).

I'm using generally the defaults, except putting in antenna type (omni), frequency (462mhz) and I'm using 50 watts for power, and the appropriate antenna heights. I've placed my mobile at the worst location I can find and Radio Mobile shows an "S4" signal strength with a 0 dBi antenna gain and "S5" with 5 dBi.

I am wondering if this is going to be enough to be copyable or will it be very static-y? Is there a generally accepted "S" signal strength that is perfectly good enough to be able to communicate on voice even if not fully quieting? If not S5, will S6 be good enough?

One thing to note is that my base is at 1500 feet and the mobile is at 820 feet, BUT there is a taller hill in between the two. Radio Mobile does not allow me to set different antenna gains for each unit (as far as I can tell), and I've tried with 0 dB, 3 dB and 5dB antenna, and 5 dBi yields the best results according to Radio Mobile. With that in mind... would we benefit from different antennas?

25 watts vs 50 watts doesn't change the "S" results in Radio Mobile and if that is the case, I'd probably go with a 25 watt radio due to price and availability (M100 for example).

I've attached the "Radio Link" image from Radio Mobile for my base and the probable worst location. Thanks.

 

[rfradioconsult]

Disregard the "S" bars, look at the green bar at the top it tells you what yo need to know, which isn't good. For your path you can expect a RX signal of -114.9 dBm and the receiver is calculated at a level of -109.5 dBm, or -5.4 dB. In other words if you received a signal at all it would pretty much be unreadable. You would need to decrease your path loss by 20-25 dB to have a usable signal.

Having said that RM or any other propagation tool is not 100% accurate, your case may be that you can talk just fine, if you are a ham try a simple test send your wife out in your car and you set up a 440 simplex frequency and make a series of test transmissions from your base and see if she can hear you. The difference in propagation between 446 MHz and 462 MHz is minimal

 

[rapidcharger]

Yeah I agree, that one you'd be best off trying first because on paper it looks impossible to get a usable signal but online maps tells a different story. Yeah I looked up your address. While there's definitely an obstruction, it's only about 2 and a half miles or thereabouts and there's some clear path along the road I presume you'd be taking.

 

[kayn1n32008]

Wirelessly posted (Mozilla/5.0 (BlackBerry; U; BlackBerry 9780; en-US) AppleWebKit/534.8+ (KHTML, like Gecko) Version/6.0.0.600 Mobile Safari/534.8+)

Radio Mobile is a VERY complex piece of software. After looking at your link profile I can see one glaring issue, and that is line loss. The more accurate the data you feed the program the more accurate the results. Your line loss on your 'surgar run' is nowhere near accuate. @ 7m (+/-21ft)you will have more than 1db of loss unless you are using reall good coax.
As well if you have adapters that loss will go up even more.
Another suggestion is to do a coverage plot rather than a point to point link. This way you can 'see' your coverage, and based on real world results adjust settings to reflect real world results, thus making the plot closer to reality. A member I know on here has spent a lot of time fine tuning RM based on real world verification of plots he has created.