72mhz formulae

[9VDXN]

Just need to confirm with those who know, the calculations for 72mhz frequency/channel number is xx x2 minus 21 right???

Eg.... Freq flag is 20...so 20x2 = 40 minus 21 is 19.

Thus for a Freq flag of ch20, actual frequency is 72.190mhz right???

Read that somewhere, but just can't find the source again...so need to confirm.

[almtmd]

72Mhz Band

Ch Mhz
15 72.090
16 72.110
17 72.130
18 72.150
19 72.170
20 72.190
21 72.210
22 72.230
23 72.250
24 72.270
25 72.290
26 72.310
27 72.330
28 72.350
29 72.370
30 72.390
31 72.410
32 72.430
33 72.450
34 72.470
35 72.490
36 72.510
37 72.530
38 72.550
39 72.570
40 72.590
41 72.610
42 72.630
43 72.650
44 72.670
45 72.690
46 72.710
47 72.730
48 72.750
49 72.770
50 72.790
51 72.810
52 72.830
53 72.850
54 72.870
55 72,890
56 72.910
57 72.930
58 72.950
59 72.970
60 72.990


Thanks

[9VDXN]

yes...the formular is correct... thanks!

[Guest]

Hi got something to enquire... Seems like there are lots of 72mhz flyers in this forum but i read it from somewhere that higher frequency has less propagation power. So why do we still use 72 mhz instead of 29mhz??? Pls enlight me...

[9VDXN]

Propagation power is relative to transmission power.
Technically it is not important to be bothered about this issue because the transmission range at 350~500mW output (for most cases of tx specs) is probably further what your eyes can see at either frequency.

Lower frequency would also mean that your transmission can be more easily be affected by RF noise...pros & cons.

[9VDXN]

also, lower frequency would mean that the signal have lesser bandwidth, thus cannot carry more stable 'info'.

Although it's not technically proven, I think that is why PCM was originally developed & meant for 72mhz operation. Can't remember where I came across this info, coz i got no proof to back up this claim.

[Guest]

hey thanks for the info!!! Very informative!!! Hey how come u know so much ah??? can give me some tips....

[9VDXN]

Read a lot..

I'm not formally electronics engineering trained, but playing with audio waveforms & RF for Radio/TV/satellite transmission is kinda related to my work...so i gotta know a few tricks or two.

Moreover, one of my interests/hobbies was Amateur Radio as well, so all the more i am interested in this field. If u look carefully, it's all back to basic physics which you've learnt in Secondary school....just gotta know how to apply them to certain things in real life.

[Guest]

Oh ok!!! no wonder you are speaking like a pro like tat