Re: Topband: RIG PROTECTION FROM BEVERAGES
Wayne, I am using the home made KD9SV front-end saver for long time on receiver input and I have never any troubles with blowing the receiver input port. Fast high quality relays is th key, just to think about the protecting diodes of the relays which are commonly used in these kind of circuits. I am not using them in order to avoid IMD issues. Regarding the lightning / storm protection I am always disconnecting coax feedlines from radios and grounding them OUTSIDE the house. It is uncomfortable a bit but the most secure for equipment I think. Hope it helps, 73 - Petr, OK1RP On Wed, Jan 16, 2013, at 04:22 PM, Wayne Willenberg wrote: > As I originally explained in my first post on this subject, I have the 75 > Ohm feedline from my Beverages connected directly to the antenna input on > my FT-5000. I thought I should be concerned about lightning protection > and > the destruction of at least the front end of my receiver. > > > Thanks to several of you who responded, I now know the larger concern > should be the Beverage feeding my transmitted signal back into the > receiver. This is probably of particular concern since I always use my > linear at about 1500W when transmitting. > > > However, no one proposed a solution. > > > I have been looking on the Internet, and one possible solution is Array > Solutions Model AS-RXFEP, RF Front End Protector. The advertising claims > to protect in the feedback situation as well as in a lightning situation. > The insertion loss is claimed to be only 0.3dB. For only $55 this seems > like a good investment. Does anyone have experience with this unit or > would you please suggest an alternative? > > > Thanks again for your help. > > > 73, Wayne KK6BT > _ > Topband Reflector -- "Noses out of the screens and back on the radios!"(G3VTT) "See You on the wireless"(G3ZWH) _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
On 2013-01-16, at 10:22 AM, Wayne Willenberg wrote: > > Thanks to several of you who responded, I now know the larger concern > should be the Beverage feeding my transmitted signal back into the > receiver. This is probably of particular concern since I always use my > linear at about 1500W when transmitting. Hi Again Wayne, I assume that by "...antenna input" on your transceiver, you're referring to a RECEIVE ANTENNA ONLY jack (probably RCA-style) at the back of the rig...? (My assumption must be correct, otherwise you're using the Beverage for BOTH transmitting and receiving---very doubtful!). Anyway, assuming that it's a receive antenna ONLY port that you mean, take a close look at the schematic of your rig: I'll wager that---being a Yaesu---the jack is automatically grounded whenever you go into transmit mode, and by extension, you can save yourself the $$$ required that it might otherwise have taken in purchasing an after-market grounding device for your station... I emphasize "Yaesu" here only because I own both a Yaesu FT-980 as well as an Icom 751A, both of which were made only a few years apart in the late 80's: when I ran my linear with the Yaesu exciter, and using a Beverage receiving antenna, I experienced no difficulties whatsoever---however, when I put the 751A in line with the amp & the Beverage, the transmitting envelope displayed on my Heathkit SB-610 monitorscope was shockingly atrocious. Of course, I used the separate receiving antenna port in each rig on both of these occasions, and pondered the whys & wherefores of the difference...until such time as I looked closely at the Icom schematic, & discovered to my surprise that the separate antenna port was NOT grounded at all when in transmit mode...and that the QRO emitted by the linear was being picked-up by the Beverage, and sent right back into the Icom, creating untold misery with RF feedback. It is my understanding that other Icoms exhibit this same shortcoming in their design. A homebrew external relay box here solved the problem for me: it utilizes a 12 VDC relay that is activated by the 751A, and which grounds the receiving antenna whenever I transmit. Total cost of the fix...? ZERO dollars---this is where an ample "...junque box" (and innate stinginess!) can pay dividends, however small... Hi Hi ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
On 01/16/2013 10:22 AM, Wayne Willenberg wrote: I have been looking on the Internet, and one possible solution is Array Solutions Model AS-RXFEP, RF Front End Protector. The advertising claims to protect in the feedback situation as well as in a lightning situation. The insertion loss is claimed to be only 0.3dB. For only $55 this seems like a good investment. Does anyone have experience with this unit or would you please suggest an alternative? You can build a near-equivalent to this yourself. You want two series of 4 or 5 schottky diodes between the signal and ground, in opposite sign to each other. This limits the maximum voltage across the radio's signal input to 2V or so. Secondly, you want to limit how much current flows through the diodes, so they are protected. You can do that by having a 5 to 10 ohm resistor in series with your signal, between the beverage antenna and the point where you have the diodes to clip the signal. That will limit the current to a small enough amount that the diodes should not get damaged, and the voltage should not go up just because there is a higher current flowing through the diodes. If you want to protect this circuit from higher potential discharges (eg. nearby lightning strikes), you can always put a TV coax gas discharge tube protection device between your the antenna and diodes+resistor circuit. Another solution is to have a relay that switches your beverage in and out, based on one of the signals put out by your radio when it receives (or transmits). Chances are the amplifier or transverter control port on your radio will have a suitable signal. _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
I have been looking on the Internet, and one possible solution is Array Solutions Model AS-RXFEP, RF Front End Protector. The advertising claims to protect in the feedback situation as well as in a lightning situation. The insertion loss is claimed to be only 0.3dB. For only $55 this seems like a good investment. Does anyone have experience with this unit or would you please suggest an alternative? I would be careful of that device. It uses back-to-back diodes. That limits the overload level to around 1/2 volt. This might be OK if you are in the middle of the ocean somewhere, but it won't be OK with antennas that pick up any BCB stations. Remember ALL signals the antennas pick up add together. The peak voltage of everything typically sums. If you can hear stuff on a crystal set, it will turn on the diodes. Even if you can't, enough weaker signals will turn on the diodes. On a second more important note, lightning arrestors have very limited value. Entrance grounding methods are probably around 90% of the cause or cure of major damage. The only safe way to protect receivers is to disconnect them, and that only works if the entrance system is correct. 73 Tom _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
> > On 2013-01-15, at 4:25 PM, Wayne Willenberg wrote: > > > I have my 2 reversible Beverages receive antenna input on my FT-5000. If > > high voltage should get induced by lightning, isn't it going to fry at least > > the front end of my receiver? > > > > How you you provided for this possibility? For lightning protection I use Polyphaser Devices on all Coax entering the house including lines from Beverage antennas. You also have another situation to think about. That is killing the front end of your receiver with your own transmit signal. Unless in your W8JI setup is also included some fast relays to disconnect and ground the RCV only input during transmit cycle. If you need one take a look at the KD9SV Products for Front End savers several also incorporate Preamps and switching for various Rcv antennas. Within the front end saver device is also arrangement whereby if the Relay that removes and grounds the RCV antenna doesn't work for some reason it won't allow you to key your Amplifier. John k9uwa John Goller, K9UWA & Jean Goller, N9PXF Antique Radio Restorations k9...@arrl.net Visit our Web Site at: http://www.JohnJeanAntiqueRadio.com 4836 Ranch Road Leo, IN 46765 USA 1-260-637-6426 _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
I did so much research on the construction and installation of the Beverages, I feel really stupid because I didn't think of one possibly critical aspect (nor did I see it discussed). I have the 75 Ohm coax from the Beverages connected directly to the receive antenna input on my FT-5000. If high voltage should get induced by lightning, isn't it going to fry at least the front end of my receiver? Most lightning damage is common mode. The key to preventing damage is cable and power entrance bonding, and perhaps disconnecting between the entrance panel and the equipment. I have a lot of stuff up here and links from that page: http://www.w8ji.com/house_ground_layouts.htm One side note, an RF choke will do almost nothing at all. Neither will a series capacitor (dc isolation). The frequency content of lightning energy is well up into the radio spectrum, so an RF choke looks like a very high impedance for lightning and a blocking cap looks like a low impedance. I certainly would not use a high value choke. If I used anything, I would stay down around 50-100 uH and use a "dam" heavy choke. How you you provided for this possibility? At the antenna, the DXE stuff intentionally has close spacing between washers and the metal cases. This forms a spark gap. The gap works pretty well for close hits if you ground the case to a separate ground rod from the signal ground. Not much helps a direct hit. In the house, for many years I had nothing at all except grounding feed throughs. I never disconnected the receiving antennas. But I have long buried cables, good grounding barriers, and my stuff runs through a multicoupler system that uses the same preamps DXE sells. The only in-shack damage I ever had, and I get dozens of local hits a year on my tall towers, was occasional mica capacitor failure or inductors opening in my BCB notch filters. These were 300 volt micas and miniature inductors. Because storms are more violent now, even to the extent of vaporizing Beverage wires, I recently added low voltage gas discharge tubes in my multicoupler ahead of the BCI filters. Lightning is a very good reason to not use inexpensive plastic boxes. I have many pitted aluminum and stainless boxes, where arcs flashed from the stainless washers to the case, and the electronics inside stayed good. Almost all of any failures I have are where a conductor melts. Either a shield blows open, or an actual antenna wire disappears. I've tried low voltage gas tubes at the antenna equipment, as well as MOV's on control lines, and I'd say any improvement is there, but is also what I would call marginal. There is a HUGE difference between plastic cases and metal, however. Since I'm a cheap skinflint Ham with limited time like most of us are, the fact I take the time to bend and use metal (or even use double-sided copper PC board cases) speaks volumes of my own experience with damage using different materials and construction methods. 73Tom _ Topband Reflector
Re: Topband: RIG PROTECTION FROM BEVERAGES
On 2013-01-15, at 4:25 PM, Wayne Willenberg wrote: > I have my 2 reversible Beverages (designed by Tom, W8JI and sold by DX > Engineering) installed and am thrilled with their performance! Now I can > listen in 4 directions, one at a time of course, with greatly reduced > noise. Stations I could never work suddenly pop out of the noise when I > switch to the Beverage. > > I did so much research on the construction and installation of the > Beverages, I feel really stupid because I didn't think of one possibly > critical aspect (nor did I see it discussed). I have the 75 Ohm coax from > the Beverages connected directly to the receive antenna input on my > FT-5000. If high voltage should get induced by lightning, isn't it going > to fry at least the front end of my receiver? > > How you you provided for this possibility? Hi Wayne, Obviously you do not employ any sort of an "isolation" (matching) transformer between your Beverages & rig...? I wonder what harm (or good...?!) installing a 2.5 mh. RF choke might do for you, placed right at your rig & connecting the centre conductor of your coax feeder to ground...? Remember the 2.5 mh. choke that's installed right at the antenna output of your linear amplifier...? Your amplifier doesn't even know it's there, until such time as the output coupling capacitor in the lead to your pi tank might short-out, whereupon the RF-blocking capabilities of that choke would be exposed to DC, and in so doing serve as a direct short of your B+ voltage to ground, blowing your fuse... In theory, I s'pose, a lightning strike---a surge in DC voltage in your Beverage feeder---would act in the same manner, passing that DC surge directly to ground, as well... OK all you gurus, experts, Poindexters, weisenheimers, & brainiacs out there reading this---LET THE FLAMING BEGIN...! :o) ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector
