kidphc Posted June 2, 2020 Report Posted June 2, 2020 I had done some SWR readings for a mag mount Nagoya UT72, Btech/Baofeng recommends for the GMRS radios. They do suggest using a proper NMO mount and another antenna. I am installing an Yaesu FTM400XDR and had picked up a Larsen/Pulse 2/70SH for use with that radio. So why not do a small review. I will continue adding to this review as I get more info. I will be getting the Larsen 2/70b in the future. Larsen Pulse 2/70 SH (link goes to dx engineering. Why, because Larsen's page is a bit of garbage) Vital stats:Mobile Antenna BandFrequency Coverage RangeVertical Antenna GainElement Phasing (wavelength)2 meters144-148 MHz2.1 dBi1/270 centimeters440-450 MHz4.0 dBi3/4 Larsen NMO mount Nothing special. Standard 3/4 drill through NMO. It was between this and the Laird NMO. Comes with 17 Feet of RG58. You will need to have a PL259 connector or N type fitting, with appropriate splicing gear. Here is a visual representation of the Larsen 2/70SH 1/4 NMO next to the Nagoya UT72 mag antenna. Notice how the Larsen (front) is a bit shorter looking. It is because of the way the NMO mounts versus the magnetic mount. It should be noted that a big CON of the Nagoya UT72 is you can not simply swap out the antenna on it. The connection of the base the location of the loading coil all cause it to be a real pain to find something else. If you go with a magnetic mount make sure it is an NMO style magnetic mount, so you can swap antennas out. Keep in mind the Nagoya UT72 is about $26 where a decent magnetic NMO without antenna is usally twice that price. Quote
kidphc Posted June 2, 2020 Author Report Posted June 2, 2020 Here is the view from the roof rack level. The Nagoya UT72 (rear) has the loading coil in the base. Which I believe was contributing to the large amount of Picket fencing issues I was having. Note the Larsen (front) has the loading goin mid way up. I am hoping for less picket fencing and reception issues from the antenna due to the design differences. Quote
kidphc Posted June 30, 2020 Author Report Posted June 30, 2020 Nagoya UT72 on baking panThe stats from BTech 's website:https://baofengtech.com/NAGOYA-UT-72 144.562 National 2m SWR 2.53 :1144.000 MHz SWR 2.89:1147.999 MHz SWR 2.21:1159.300-163.500 lowest SWR of 1.18:1 420.000 SWR 1.92:1450.000 SWR 1.33:1444.900-445.800 lowest of SWR of 1.3:1 FRS/GMRS Frequencies462.5625 SWR 1.35:1467.7250 SWR 1.40:1 Nagoya UT72 on truck with about 20" of ground plane in all directions. Loading coil is below the roof rack. 144.000 MHz SWR 1.90:1147.999 MHz SWR 1.3:1 Lowest (148 MHz) SWR of 1.3:1 420.000 SWR 2.28:1450.000 SWR 1.36:1Lowest (447.3 MHz) SWR of 1.3:1 FRS/GMRS Frequencies462.5625 SWR 1.13:1467.7250 SWR 1.48:1 Quote
kidphc Posted June 30, 2020 Author Report Posted June 30, 2020 Larsen 2/70SH 144.000 MHz SWR 1.37:1147.999 MHz SWR 1.14:1 Lowest (146.96 MHz) SWR of 1.09:1 420.000 SWR 1.77:1450.000 SWR 1.44:1Lowest (444.6 MHz) SWR of 1.18:1 FRS/GMRS Frequencies462.5625 SWR 1.59:1467.7250 SWR 1.48:1Lowest (466.320) SWR 1.44:1 (doesn't matter out of band) Quote
kidphc Posted June 30, 2020 Author Report Posted June 30, 2020 Larsen NMO 2/70B (Untuned) 2 meters 144-148 MHz 3.8 dBi 1/2 70 cm 440-450 MHz 5.2 dBi 1/2 + 3/8 144.000 MHz SWR 1.14:1147.999 MHz SWR 1.86:1 Lowest (144.4 MHz) SWR of 1.11:1 420.000 SWR 1.88:1450.000 SWR 1.82:1Lowest (438 MHz) SWR of 1.06:1 FRS/GMRS Frequencies462.5625 SWR 2.68:1467.7250 SWR 2.52:1Lowest (465.750) SWR 2.51:1 (doesn't matter out of band) Quote
kidphc Posted June 30, 2020 Author Report Posted June 30, 2020 Now for the ear subjective test. Larsen NMO2/70B (open coil variant)The longest antenna out of the three, it is the thinnest of the the 3 antennas. Many antenna designers have a very similar or identical design. Don't let the SWR numbers fool you. This antenna due to the height and gain numbers easily hears repeaters and FRS users from far away. Although, mobiles can handle high SWR numbers better it is really starting to get border line. There is much less picket fencing (signal going in and out when moving), easily gets out further, when compared to the Larsen 2/70SH. A 2m repeater (60 miles away) was starting to break squelch but could not be copied with the 1/4 variant. Yes, the repeater is doing all the work, but it was annoying to have squelch breaks of white noise constantly. With the 2/70B I am able to make out copies with heavy to moderate hashing. The 2/70B, I am hearing a lot more FRS/GMRS users about, and can actually hear them. Not sure if I want to risk a radio transmitting on GMRS/FRS with it though. In a real emergency "F" the radio. It does wag around like a dog tail over every bump, I have yet to notice any ill effects due to this. Because of the flexibility, this will probably survive the longest, and I believe the NMO will rip out first. Because of how happy I am with this antenna, I am eyeballing 60" super gain antennas for the long trips up to Toronto through the mountains. A huge negative to many, you gotta look at drilling to maximize this antenna. Larsen 2/70SHThis little 1/4 wave has a spring built into the base. The coil is about half way up the antenna clearing the roof rack. It is an enclosed type, so an eyeball needs to be kept on it as it gets older, to avoid water/ice buildup inside the coil wrapper as it ages.The whip is sturdy, it is about 8-10 gauge in diameter. Did I mention the beefiness. It out performed the UT72 on reception and transmitting. There was still a fair amount of picket fencing, I was starting to believe I couldn't do much about the multi-pathing. However, this antenna out shines the UT72 in reception. It was able to pick out signals 2-3 miles further out then the UT72. The 2/70sh is a keeper, for the trails and around town with low obstructions. When compared to the UT72 I believe a lot of the differences has to do with the coil location (couldn't get a clear view with the UT72) and the ground plane NMO vs magnetic mount. A huge negative to many, you gotta look at drilling to maximize this antenna. Nagoya UT72The UT72 hears the least and gets the most static. It also has the most amount of picket fencing . I believe it is because the loading coil is built into the magnetic base. Which on my truck is below the roof rack. The big negative is that you can't swap out the antenna, since the magnetic mount uses and N style female connector. I may try in the future to get a ht whip and adapter. The pro, the cheapest and easiest to deploy, since with the base the antenna is about $27. Also the antenna base incorporates a spring. The antenna is fairly stiff, I have managed to knock off the magnetic mount when the spring failed to give enough, it is loud when this happens. SUMMARY A lot of the differences between the different antennas come down to ground plane and loading coil locations. Not so much who makes the better antenna. Really in honesty, that will change with materials and how it was designed. I choose Larsen, since every one of the antennas and NMO has parts available from the manufacturer. Not all manufactures will have parts available much less sell you every component. Either way you will see similar results with similar style antennas. So net effect, listen to the old timers, Break out the drill, and get yourself a nice SWR meter to maximize your antenna. Quote
kidphc Posted July 7, 2020 Author Report Posted July 7, 2020 *** UPDATE There was some concern about the fact that the NMO2/70B might have been a fake. The order was validated with Gigaparts as an original. Not sure if there are differences (material etc) from the original Larsen and the post merger PulseLarsen antennas. They say nothing has been changed. They did say not to tune the antenna due to the design. If I tune for 460 it will bring the 2m band out of tune. Due to the fact that the 460mHz band is about 10 mHz out of design band. The SWR looks about right, the more you get out of tune the faster and higher the VSWR climbs. if you are looking for something closer you may want to try something that has a wider range on 70CM or tuned up to 460 mHz. This is a reactance and SWR chart from some one who tested the antenna only on 2m. The SWR looks about the samehttps://forums.qrz.com/index.php?threads/larsen-nmo-2-70-swr-reactance-chart-plus-a-tuning-question.562729/ Quote
WRJA503 Posted February 21, 2021 Report Posted February 21, 2021 so I just compared today my Larsen 2/70SH vs a Comet 2x4sr, both using the same NMO mount, center truck roof, brought down to the radios by LL-195 cable, good connectors.The comparison method was a passive field strengh meter whose antenna was tuned at 1/2 wavelength of GMRS at 467MHz, since that is roughly the repeater input frequency of interest. The field strength meter was not touched except to slightly move it around in case of a local null/peak that might bias the test. No such effect was observed. Basically the Larsen put out so much less power than the Comet, as witnessed by the field strength meter, it was shocking. Even at 440MHz, and adjusting the field strength meter antenna to closely match the 440MHz wavelength, the meter needle would barely move, whereas with the Comet and that same field strength sensitivity setting, the needle would nearly get pinned to 100% on 440 and 467. I had to check the Larsen at 2m to make sure something was not messed up, and at 144MHz, the meter needle would response well so the Larsen antenna is 'working'. The Larsen in this setup had decent SWR in VHF, UHF and GMRS bands, so it reminds that SWR doesn't mean that all that forward power gets transmitted as effective RF energy.The only variable again, in my test, was one antenna vs the other. All cabling, radio tx unit, all the same. In terms of real world performance, the Larsen on UHF 70cm stations, well I can hit them all well, and hear them well, but in terms of comparative EIRP, the Comet smokes it in the UHF department.The Comet is also alot longer and I simply can't use it on my roof as the antenna would have to be taken down (using the hinge) which is a hassle that I put up wtih for a while, but even though the Larsen is less efficient at 70cm, it doesn't require me to get my lazy butt out of the truck to garage the vehicle. The antenna bends nicely and snaps back as it drags under the raised garage door. But If I need maximum GMRS performance or UHG performance, I know where to put the Comet and switch cables etc to achieve maximum performance.p.s. right now the Comet is on the back right corner of my bed, mounted in a modified Breedlove mount (I replaced Breedloves connector since it seems to increase SWR) with an ARCANTENNA NMO LL-195 cable kit. That surprisingly puts out 50-60% of the power that the Comet does on the roof center NMO. HOWEVER... that does not hold true in front of the truck... the cab not surprisingly kills alot of the signal, so if you need to operated GMRS with a Comet in such a position, make sure your repeater is behind the cab basically. Quote
mbrun Posted February 21, 2021 Report Posted February 21, 2021 I love the fact that you got the field strength meter out to contrast the two antennas. ...The comparison method was a passive field strengh meter whose antenna was tuned at 1/2 wavelength of GMRS at 467MHz, since that is roughly the repeater input frequency of interest. MichaelWRHS965KE8PLM Quote
n4gix Posted February 26, 2021 Report Posted February 26, 2021 The body of the vehicle affects the lobes of the signal leaving the antenna, which why the center of the roof is the best choice. Having the antenna mounted on the right rear means that the major lobe will be focused on the right rear of the vehicle. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.