wqzw301

Can you diplex a powered antenna. / vhf ----[ Lna ]------ / \ rx only---------- [+12v (tee)]------[uhf/vhf (diplexer / band split)] dual band antenna \ / \ / uhv------------------- Please and thank you for any help wqzw301

Hello all, Does anyone know if it is possible to lower the wattage output on a radius M1225? I read in repeater-builder that an m1225 was a good exciter for a (stand alone) msf-5000 pa . The Msf-5000 has an input of >5watts give or take.... I do have the rss (windows xp) for the Motorola m1225, I'm thinking, there might be a way, to adjust output wattage, in the service feature? Also I've read in forums (years ago) that people would adjust the m1225 potentiometer, when programming out of band, for ham use.... I'm putting together a repeater in the vhf business bands. I was also thinking an inline attenuator, but that kinda defeats the purpose of increasing the duty cycle, even on low,15 watts...just more heat generated that needs to be exhausted. Please and thank you for any help you can give me in this matter. d

So this is what I got, on the rf side of things... Motorola Radius M1225 UHF 20-40watt ID o Matic controller RG-214 jumpers with N (non magnetic - nickel free) connectors LNA from Downeast Microwave GaAs Phempt >17db gain 0.5db noise figure. Harmonic Preselector 3 pole - 1.2 db loss - pulled from a Motorola MTR2000 brick Vertex 6 cavity XUFIP0001 notch duplxer . 40watts in 37watts out on my meter. 50ft of DX Engineering 400max to a slim jim 3/8" copper - mounted on a 40ft fiberglass mast - away from all things metal... My question Should I add a Low Pass Filter? I kinda want to.... I've used them before on vhf transceiver's and have had great success in the cell tower jungle of Brooklyn.... BUT...Is there a point where more becomes less.....in line to the receiver My neighborhood did just get new 800mhz cell towers in the area. About 1/4 mile away.... I have a LPF pulled from a GE Harrison repeater (432 - 470mhz). Can't find specs for it. Don't know the db loss... I am looking forward to experimenting.....but due to my situation, I can not run around with an ht right now... Plus I have learned on my own and would like to hear from people who actually know what they are doing and can add to my knowledge... thanks d

I recently tried lmr240 instead of rg8x. Works great, better weather protection and shielding. Also less db loss than 8x on the TIMES MICROWAVE coax comparison chart for uhf... Just a bit thicker but still pretty flexible. My snap on ferrites fit the same as on rg8x. Also I went with N connectors instead of UHF. good luck 301

Here is the situation... I have a N9TAX dual band antenna, 40ft above ground (20' above my roof) Fiberglass mast. 25' run of lmr400 and a pair of mix 31 and mix 61 snap on ferrites All UV and weather proofed. Access to adding an antenna is difficult. Swr is good on gmrs and murs. My brother has a fishing boat. I have an Icom marine radio, when I use the radio on the antenna, ship to shore channels, SWR is above 3. I recently picked up a winning bid (on line) for a MFJ-921 VHF 144-220 MHz. Antenna tuner- $50. There are a lot of opinions on forums, about, not using a tuner on upper vhf bands....most opinions are to just properly tune your antenna since mismatched feed lines and large antennas aren't an issue on that portion of the vhf band. But not really addressing any problems that might be incurred if actually tried..... The icom marine is only 25 watts and the swr isn't too high, but I still would prefer not to punish an expensive radio on high power... To my knowledge the tuner just matches the impedance at the end of the feed line within the radio's tolerance. Which is all I am looking for -protection. I know swr doesn't per se, effect performance. I believe the loss going through the tuner is around .5 db..... Any opinions on this idea? Before I get started with this experiment.... MFJ-921 is a manual tuner. Plus I am studying for my Ham ticket, so if this is an option, it might save me a dangerous climb to add/replace antennas. And I would like to keep my gmrs repeater for my family..... Please and thank you, in advance for any opinions, knowledge, expertise that you can give me in this endeavor. 301

Point of curiosity.... In the amateur radio world I noticed repeaters with negative offsets -5 mhz.... in 70cm band do you need a different duplexer, factory set for negative offset? I can't imagine that your standard cavity and notch duplexers would be able to be tuned in reverse.... for example instead of 440/445 a negative 445/440 offset.... can't find any info on this, or even experiment (do not have skills or equipment for tuning) Anyone have some knowledge in this area? thanks 301

Thanks for the info and knowledge guys Yes, both repeaters have a Morse id call sign . I believe I have all jumpers extra shielded. I think I will go with the 10ft vertical separation. I'll do some experimenting, break out the field strength meter...I have some Palomar mix 61 ferrites to try..... Thank You!

I have a repeater, Motorola 50 watt, cellwave 6 cavity band pass notch duplexer - 38 watt output after duplexer. My brother now has a repeater 50 watt Motorola with vertex standard 6 cavity notch duplexer. Our frequencies will be about 14mhz apart. mine - 462's and his - 448's I use dx 400 max coax with a slim jim He will use lmr 400 not sure about antenna??? Looking for some opinions about antenna spacing??? I have a vertical 20' pole mount on the 20' roof Should we flip a coin and see who will be low man on a vertical split totem pole???? and how far apart? or can we go horizontal with another mount??? I've heard of two repeaters sharing an antenna... but commercial repeaters set ups by bridgecom... Any recommendations??? thank you 301

I am surrounded by water.... Bay and ocean. Would the directional antenna be best? I will not be able to turn it.... I have a small skiff and my brother has a commercial boat. That's the only reason I started to consider mounting the vhf..It was an afterthought. Also I know the fcc just allowed marine vhf handheld portables to be used from shore to ship. But I'm still going to apply for a marine license for base station, with my frn on the fcc licensing sight. I just have to see what, or if any commercial info I have to provide... I would like to use maybe even experiment with building a directional, but on the roof, with no access??? thanks 301

PastorGary thank you very helpful. I think I've heard somewhere that every foot of vertical separation is equal to 10ft of horizontal separation ??? But I'm not sure if that applies to every frequency.... thanks 301

Hello All, I could use some expertise. I'm putting up a mast on my roof - 8ft fiberglass. I am mounting a j-pole on top, tuned to my repeater frequency... I also have a 1/4 wave marine vhf, I was going to mount below the uhf j-pole. But I started thinking....the marine antenna would be use, only sporadically, to contact my brothers boat. The antennas would not be used simultaneously...vhf mostly for bad weather check ins.... Can I mount them side to side on top of the pole? The pole has a 1 1/2 dia. and I can mount both without contact. I know vhf antennas should be on top of the stack, but the vhf is just an addition and I have great line of sight to the ocean...but can they be mounted side to side? and if so - One radio would have to be off while transmitting on the other, because I would be putting rf down the other radios coax -correct???? thanks for taking a look guys 301

never mind I got cps thanks

Does anyone know a shop in the nyc area that can do programming of Motorola Radius Mobiles. I just purchased a couple of m1225's for $30 each. Great output and clarity on the channels programmed in on business band. And yes I used a dummy load.... I know there are ebay'er who offer the service...but would prefer to use local business... thanks. The Motorola retailers I looked up in nyc deal with only big service contracts and new products...not a 20 year old synthesized fm uhf transceiver with leaking capacitors thanks 301

Hello all, This fall I'm having a roofer do some gutter work....Thinking of asking him to mount an antenna for me. Does anyone have any ideas on a good antenna and mount??? I was looking at diamond antennas.... I have a gmrs repeater and also occasionally use vhf so I was thinking dual band..... Would anyone recommend using two antennas uhf and vhf. I use the vhf only ,now and then, for MURS and Marine. 1/2 wave on uhf has worked the best for me in my area.... In the mean time I am using a 1/2 wave j pole slim jim I made from ladder line... on a 40ft fiberglass telescoping pole. I was thinking maybe ground plane for the roof....I do like j poles tho...... thanks 301

Working great now. Thanks Lads! Celwave notch duplexer (tuned correctly) was the last piece of the puzzle.... I hit my repeater from 5 miles yesterday on a walkie - inside a bus.... Going to do some more upgrades. I purchased a used 19" 6u rack enclosure from ebay. Going to build and isolation box for the receiver. Replace jumpers with dx engineering 400 coax double shielded and silver plated brass connectors. Added a Sec 1235 30amp switching power supply to help run some fans... I also added a station Id from an old surcom siplex repeater circuit connected to the RICK. Thanks for all your help, everyone! I learned a lot and had fun! 301

Radioguy7268, I'm in Brooklyn very south and east, no buildings just houses, by the water... Very little rf interference. The only uhf rf 70cm is the nypd / fire / ems repeaters on a couple of telephone poles and vhf from Airplanes, Kennedy Airport and marine channels. People don't even have driveway door remotes.... Nearest cell tower is 1 mile. But lots of above the ground electrical wire on telephone poles.... We have about 3 gmrs repeaters and 5 ham 70cm repeaters. But Brooklyn is huge... We can fit 2 1/2 London's or Berlin and France together inside Brooklyn..The repeaters are all spaced far apart. It's not like Manhattan at all. We have a saying in Brooklyn - Keep Brooklyn low and local.... No tall buildings and no Wal-Mart. My antenna is 45ft high. which is 20 ft over my house. Only a couple of drive thru about 3 miles away that broadcast on .5 watts murs. Just mom and pop stores that most don't even take debit card..... I'm in the sticks of Jamaica Bay...I'm by a 25 square mile national park made up of wetlands sparse trees. I work in Manhattan and can hit my repeater 20 air miles from the 28 floor roof deck my friend is the super of...5 watt hand held.

Berkinet, Are notch band pass duplexers supposed to be tuned to a specific frequency set?? I see a lot of them sold with a range and no mention of being tuned like notch only duplexers. p.s love Marcus Aurelius.. Great quote!

Sorry Guys, been a busy last week. So I went through everything and couldn't find the problem..... I took repeater apart....using a simplex repeater (parrot) on both radios ...I'm able to transmit and receive from 5-7 miles (same antenna).... physically going on road trips with my hand held I think its the duplexer....notch 4 cavity. Looks like it is tuned for both .575 and .600.... plus made in china... I am saving up to get an American made duplexer but in the mean time, I just traded a radio for another Chinese duplexer, new and 6 cavity, that is being tuned to .575 specifically. Also, In the mean time I just ordered all new coax and adapters from dx engineering . Double shielded antenna coax and jumpers. Plus waterproofing...So I'm going to take the time to upgrade wiring... dx engineering 400max coax and silver plated brass connectors. Plus I just had an idea. I have a small DC/AC mini fridge (for tailgating, weighs 10lbs) I never used it. I'm using it to house the whole repeater... I all fits and will keep the tx radio, amp, power supply cool, plus it looks kinda cool. I started building an isolation box (copper lined) for the rx radio, inside 2nd shelf. Also thinking about a preamp circuit.... Thanks for all the help! will keep you posted Thanks! 301

Hello, Repeater transmitter is a Motorola Radius. Receiver is an HT1225 board. I've had the 4 cavity band reject Duplexer professionally aligned to the programmed frequencies. ​15 watts and 1.2 on swr -with my outside mast antenna. ​Works well within about 500 yard radius....... ​ Using another transmitter alone on simplex, same frequency, power(15 watts) and same Antenna, I have at least 5 mile range between base transmitter and my mobile 25 watt car transmitter. ​Any thoughts on what is going on here??? The only scenario Ive come to is the old Motorola is wide band and being used with new narrow band transmitters and receiver's. But even when I've reprogramed the newer radio's to wide band - very little improvement. Reception is just as bad. I have replaced all the connectors and coax..... ​Since the performance of the Radius repeater and simplex transmitter are so different on same antenna and power output...... ​If anyone has any thoughts on this problem, it will be appreciated ​Thank you, ​301