October 2013 - AMSAT-BB - mailman.amsat.org

[Re: AMSAT-BB NF formula posting (amended)
by i8cvs 05 Oct '13

05 Oct '13

Hi Ralph, W0RPK and All on the list. Unfortunately in my previous message i have taped few mistake but hopefully the following calculation are actually correct. I have rewrite the formula in another arithmetical form wich is easier to be used and not is corrupted or differently formatted sending it through BB NF = ( Vi x 10^-6 )^2 ) x 20 ) / (BW x S/N ) ) log ) x 10 ) + 174 dB 10 where: Vi = input signal in uV applied across the 50 ohm RX input BW = Bandwidth in Hz (2400 Hz for SSB) S/N = Signal to Noise ratio in power ratio The sensitivity for YAESU FT-726R of W0RPK in 2 meters is specified for 10 dB of (S+N)/N and not for 10 dB of S/N as required by the formula so that we must convert first (S+N)/N into S/N as follow. S + N S/N = ----------- - 1 = (10-1) = 9 in power ratio N Calculation of NF for sensitivity of 2 meters SSB/CW less than 0.15 uV for 10 dB (S+N)/N ........... we compute: NF = ( 0.15 x 10^-6)^2 ) x 20 ) / ( 2400 x 9 ) ) log ) x 10 ) + 174 = 7.18 dB dB 10 ____________________________________- The sensitivity for YAESU FT-726 R of W0RPK in 70 cm is specified for 12 dB of (S+N)/N and not for 10 dB of S/N as required by the formula so that we must convert first (S+N)/N into S/N as follow: S/N = ( S + N ) / N ) - 1 = 10^( 12/10) ) -1 = 15.84 - 1 = 14.84 in power ratio Calculation of NF for sensitivity of 70 cm SSB/CW less than 0.15 uV for a 12 dB (S+N)/N ratio.............. we compute: NF = (0.15 x 10^-6 )^2 ) x 20 ) / ( 2400 x 14.84 ) ) log ) x 10 ) +174 = 5.01 dB dB 10 CONCLUSION: 2 meters: Noise Figure NF = 7.18 dB 70 cm: Noise Figure NF = 5.01 dB The sensitivity voltage in 2 meters and 70 cm has the same value of 0.15 uV but in 70 cm 0.15 uV are specified for a 12 dB (S+N)/N ratio and not for a ratio of 10 dB (S+N)/N as in 2 meters and so it happens that the receiver is more sensitive in 70 cm Please note that the above formula is valid only for Vi = input signal in uV applied across the 50 ohm RX input. Unfortunately the manufacturers do not specify if Vi of the sensitivity specifications is the voltage that we read with the RF Signal Generator connected to the receiver input or if Vi is the voltage that we read over the Signal Generator with open output. This can generate ambiguity in calculating NF because measurement are made with a Signal Generator with 50 ohm impedance output connected to the receiver input wich impedance is as well 50 ohm so that the output voltage of the Signal Generator is divided in two equal parts across both the internal 50 ohm impedances. BTW many commercial receiver NF calculations are demonstrating that the value of NF match very well with the input voltage Vi so that we can assume that the manufacturers specifications are giving Vi as the voltage applied across the 50 ohm receiver input. The formulas where published into an old issue of the Ham Radio Magazine early about 1973 and I have to find it in my many papers after that I will send a copy to any one is interested to it. I use this formula very often and this numbars are burned into my brain HI HI ! Please Ralph let me know if your calculations match with the actual one ?! I hope this helps and if there is any question please let me know. 73" de i8CVS Domenico ----- Original Message ----- From: Ralph Wallio, W0RPK To: domenico.i8cvs(a)tin.it Sent: Friday, October 04, 2013 4:48 PM Subject: AMSAT-BB NF formula posting Domenico -- Thanks for posting the NF formula. Your results for the ICOM IC-R10 cause me to reconsider what I have been estimating for my much older YAESU FT-726R. Specifications from the Yaesu Operating Manual: 2m SSB/CW Less than 0.15uV for 10dB (S+N)/N 70cm SSB/CW Less than 0.15uV for 12dB (S+N)/N I would like to make this calculation myself but I am having trouble duplicating your results probably due to uncertainties resulting from how the formula is formatted by AMSAT-BB. Perhaps you have a document source to suggest that will resolve these uncertainties. TNX es 73 de Ralph W0RPK

1 0

Re: AMSAT-BB NF formula posting
by i8cvs 05 Oct '13

05 Oct '13

Hi Ralph, W0RPK I will write the formula in another arithmetical form: NF = ( Vi x 10^-6 )^2 ) x 20 ) / (BW x S/N ) ) log ) x 10 ) + 174 dB 10 where: Vi = input signal in uV applied over the 50 ohm RX input BW = Band Wide in Hz (2400 Hz for SSB) S/N = Signal to Noise ratio in power ratio = 10 Going to your YAESU FT-726 R the sensitivity is specified for 10 dB of (S+N)/N and not for 10 dB of S/N so that we must convert first (S+N)/N into S/N with the following formula: S + N S/N = ----------- - 1 = 10 log (10-1) = 9.54 in power ratio N 10 Calculating the sensitivity for 2 meters SSB/CW less than 0.15 uV for 10 dB (S+N)/N we have: NF = ( 0.15 x 10^-6)^2 ) x 20 ) / ( 2400 x 9.54 ) ) log ) x 10 ) + 174 = 6.9 dB dB 10 ____________________________________ Calculating the sensitivity for 70 cm SSB/CW less than 0.15 uV for 12 dB (S+N)/N we have: S + N S/N = ----------- - 1 = 10 log (15.84 -1) = 14.84 in power ratio N 10 NF = (0.15 x 10^-6 )^2 ) x 20 ) / ( 2400 x 14.84 ) ) log ) x 10 ) + 174 = 5.01 dB dB 10 CONCLUSION: The sensitivity in 2 meters and 70 cm is the same 0.15 uV but in 70 cm 0.15 uV are specified for 12 dB (S+N)/N and not 10 dB (S+N)/N as in 2 meters and so it happen that the receiver is more sensitive in 70 cm The formulas where published into an old issue of the Ham Radio Magazine early about 1973 and I have to find it in my many papers after that I will send a copy to you but I remember it very often ant this numbars are burned into my brain HI HI ! I hope this helps and if you have any question please let me know. 73" de i8CVS Domenico ----- Original Message ----- From: Ralph Wallio, W0RPK To: domenico.i8cvs(a)tin.it Sent: Friday, October 04, 2013 4:48 PM Subject: AMSAT-BB NF formula posting Domenico -- Thanks for posting the NF formula. Your results for the ICOM IC-R10 cause me to reconsider what I have been estimating for my much older YAESU FT-726R. Specifications from the Yaesu Operating Manual: 2m SSB/CW Less than 0.15uV for 10dB (S+N)/N 70cm SSB/CW Less than 0.15uV for 12dB (S+N)/N I would like to make this calculation myself but I am having trouble duplicating your results probably due to uncertainties resulting from how the formula is formatted by AMSAT-BB. Perhaps you have a document source to suggest that will resolve these uncertainties. TNX es 73 de Ralph W0RPK

2 1

2m--> 10.7Mhz downconverter
by Andy Brian 05 Oct '13

05 Oct '13

Hi, I need help to find any good design for the 2m to 10.7MHz downconverter which I'll try to use for presentation linear transverter. Please if you have any or point me to any good books where to find? Thanks for all answers, BR Andy

4 3

Re: Crushcraft A144-10T "VHF Twist" Antenna
by i8cvs 05 Oct '13

05 Oct '13

Hi Les, N1LF To built a polarization switching for a crossed yagi Cushcraft A144-10 T is unpractical because the antenna and the phasing harness are using PL connectors and the coax relays are normally supplied with N type connectors. You can't remove the PL connectors from the phasing harness because they are crimped over two 1/4 electrical length of RG-59/U and one 1/4 electrical lenght of RG-58/U so that cutting and removing the original PL connectors those 1/4 wavelengt lines will became shorter than 90 degrees. BTW you can rebuild a new phasing line using six N connectors for the phasing line, two N female N barrels connectors,a N type T connector and change the PL with N flanged female connectors over the gamma match arms of both dipoles. The cost for all N connectors and coax relay will be higher than the cost of a new modern crossed yagi available with switching polarization relay as new in the USA market. Since your antenna will be mounted inside your large attic and it will stay high and dry, I suggest you to connect your A144-10 T as originally designed connecting the phasing harness for RHCP or LHCP and stay happy with the compromise results obtined. 73" de i8CVS Domenico ----- Original Message ----- From: "Les Rayburn" <les(a)highnoonfilm.com> To: "i8cvs" <domenico.i8cvs(a)tin.it> Sent: Friday, October 04, 2013 5:57 AM Subject: Re: [amsat-bb] Crushcraft A144-10T "VHF Twist" Antenna > Domenico, > > Thank you for your wise advice. Unfortunately a new cross-polarized > antenna is not in the cards right now due to budget. > > Would it be possible and practical to build a polarization switching > relay for the antenna to allow me to rapidly switch between RHCP and LHCP? > > The connectors are not an issue, since it will be mounted inside my > large attic. It will stay high and dry. > > 73, > > Les N1LF > > > > > > > On 10/3/2013 10:39 PM, i8cvs wrote: > > ----- Original Message ----- > > From: "Les Rayburn" <les(a)highnoonfilm.com> > > To: "AMSAT Mailing List" <amsat-bb(a)amsat.org>; <starcom-bb(a)star-com.net> > > Sent: Friday, October 04, 2013 4:18 AM > > Subject: [amsat-bb] Crushcraft A144-10T "VHF Twist" Antenna > > > > > >> I just acquired a "new" in the-box, never assembled Crushcraft A144-10T > >> "VHF Twist" antenna. It includes the cabling to allow the user to select > >> left or right hand polarization. My questions are numerous: > >> > >> 1.) How is the performance on this antenna, compared to more modern > >> designs? > > Hi Les,N1LF from Domenico, i8CVS > > > > 1) I have used the A144-10T since 1973 and compared to modern > > type it works no so well because the phasing harness to switch > > polarizations uses crimped PL connectors and you get water and > > humidity into it. > >> 2.) If I were going to install it inside my attic, should I chose left > >> or right hand polarization? > > 2) To switch between RHCP and LHCP you must screw and unscrew > > by hand the phasing harness connectors and since the antenna is not > > equipped with a polarization switching relay you have not the time > > to switch polarization while operating the satellite. > >> 3.) Any caveats or things to watch out for? > >> > > 3) Do not use the above Cushcraft A144-20 T for the above reason. > > Buy a modern model of crossed yagi with polarization switching > > relay between RHCP to LHCP possibly from 2M > > > >> Any information that could be provided would be great. I was thrilled > >> when a friend stopped by and asked me if I'd be interested in the > >> antenna. Good price too. > >> > >> > > I understand a good price because it is a old model of antenna > > wich designe is almost back 30 yars ago. BTW the aluminum is > > a good quality and witstand on the environment for many years. > > > >> -- > >> 73, > >> > >> Les Rayburn, N1LF > >> 121 Mayfair Park > >> Maylene, AL 35114 > >> EM63nf > >> > >> 6M VUCC #1712 > >> AMSAT #38965 > >> Grid Bandits #222 > >> Southeastern VHF Society > >> Central States VHF Society Life Member > >> Six Club #2484 > >> > >> Active on 6 Meters thru 1296, 10GHz & Light > > 73" de i8CVS Domenico > > > > >

1 0

Digital QRM on FO-29
by Paul Stoetzer 04 Oct '13

04 Oct '13

During two passes of FO-29 - at around 0120Z last night and around 1430Z this morning, I've heard some QRM that sounds like a digital signal. I confirmed that others heard it too and it wasn't local QRM, so it's obviously being relayed by the satellite. Downlink is around 435.860 MHz (I heard it around 435.865 last night as the satellite was approaching and around 435.855 MHz this morning as the satellite was moving away), so the signal is likely being transmitted around 145.940 MHz. Has anybody else heard it? Any ideas on what the source might be? 73, Paul Stoetzer, N8HM Washington, DC

1 0

Oops
by Price, Brennan, N4QX 04 Oct '13

04 Oct '13

It appears I failed to correctly identify the pass times. Thanks to NJ1H for the alert. Sadly, we'll be in bulletin mode by the correct pass times. So no luck today, but Ishmael promises to activate 8P on his return. 73 de N4QX Sent from my Verizon Wireless BlackBerry -----Original Message----- From: bprice(a)arrl.org Date: Fri, 4 Oct 2013 16:17:51 To: <amsat-bb(a)amsat.org> Reply-To: bprice(a)arrl.org Subject: W1AW to be QRV for passes this afternoon A student in this year's USTTI/ARRL Amateur Radio Administration course (Ishmael, 8P6PE) has asked to engage in a satellite QSO. We're going to take advantage of the passes we have that work with the W1AW guest operating hours. We will try FO-29 at 1845z and VO-52 soon after at 1850z. The passes have max. elevation at 10 and 11 degrees, but we should be able to see the birds from the top of the relevant tower. Mode will be SSB, and while we can't promise to QSO with everyone, we welcome all who try. Thanks and 73, Brennan Price, N4QX/1 Chief Technology Officer, ARRL Sent from my Verizon Wireless BlackBerry

3 2

W1AW to be QRV for passes this afternoon
by Price, Brennan, N4QX 04 Oct '13

04 Oct '13

A student in this year's USTTI/ARRL Amateur Radio Administration course (Ishmael, 8P6PE) has asked to engage in a satellite QSO. We're going to take advantage of the passes we have that work with the W1AW guest operating hours. We will try FO-29 at 1845z and VO-52 soon after at 1850z. The passes have max. elevation at 10 and 11 degrees, but we should be able to see the birds from the top of the relevant tower. Mode will be SSB, and while we can't promise to QSO with everyone, we welcome all who try. Thanks and 73, Brennan Price, N4QX/1 Chief Technology Officer, ARRL Sent from my Verizon Wireless BlackBerry

1 0

Space Law, Space Debris
by B J 04 Oct '13

04 Oct '13

Putting something into space is more than just building and launching hardware: http://moonandback.com/2013/10/04/space-law-in-down-to-earth-english/ http://www.parabolicarc.com/2013/10/04/space-debris/ 73s Bernhard VA6BMJ @ DO33FL

1 0

Crushcraft A144-10T "VHF Twist" Antenna
by Les Rayburn 04 Oct '13

04 Oct '13

I just acquired a "new" in the-box, never assembled Crushcraft A144-10T "VHF Twist" antenna. It includes the cabling to allow the user to select left or right hand polarization. My questions are numerous: 1.) How is the performance on this antenna, compared to more modern designs? 2.) If I were going to install it inside my attic, should I chose left or right hand polarization? 3.) Any caveats or things to watch out for? Any information that could be provided would be great. I was thrilled when a friend stopped by and asked me if I'd be interested in the antenna. Good price too. -- -- 73, Les Rayburn, N1LF 121 Mayfair Park Maylene, AL 35114 EM63nf 6M VUCC #1712 AMSAT #38965 Grid Bandits #222 Southeastern VHF Society Central States VHF Society Life Member Six Club #2484 Active on 6 Meters thru 1296, 10GHz & Light

6 5

Stacking LEO and Terrestial antennas
by Dean Maluski 04 Oct '13

04 Oct '13

I have a pair of antennas, 440 and 2 meter LEO typical setup with G-5500 rotor and fiberglass horizontal boom. It is mounted about 18 inches above top of tower on vertical mast. I can probably push it up another 1.5 feet before having to add on to vertical mast. I would like to also hang a Cushcraft A3S a couple inches above top of tower on mast. I think the back of 2 meter antenna is about 5~6 feet that rotates downward when chasing LEO's. The reflector on A3S dimension is 7 feet horizontally from mast. I'm wondering if anyone has a setup similar to this and if there are is a negative impact of antenna proximity? I haven't bought the A3S yet. Want to be fairly comfortable this will work OK before I make the investment in the A3S HF Yagi.

1 0