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I can claime I have a two foot long dick.All the wimmins around the
World would be beating a path to my door.If they come (CUM) here,I would turn the table upside down and tell them to help themselves. cuhulin |
do you know how to spell ? (besides being gross)
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I think you should buy the preamp if you think you will like it. I think
that the reason nobody on this NG seems to have the Kiwa preamp is because they all have decent receivers. With a halfway decent receiver, you don't need a preamp. The trend in recent years has been to use NO RF amplification ahead of the 1st mixer. In the tube days, an RF amp was generally needed, because of the use of pentagrid convertors, etc. Exceptions were the R390 (at least the 1970s unit I had), which used a 6C4 1st mixer, the Squires Sanders IBS Superhet and their amateur version (SSR-1 or SS1-R?), which used a 7360 balanced mixer. If you have a good NF, there is no need for a preamp. A case in point...........even though the Kiwa preamp, which is very good, has an IP3 of +34dBm, the gain that the preamp provides still degrades the IP3 of the receiver itself by that same amount. +34dBm is ok for a high level preamp, but it is possible to design an RF preamp that has a +40dBm IP3. In all fairness to Kiwa, the preamp is very reasonably priced. I once looked at a schematic of the regenerative preamp for the Kiwa loop.............a very good design. The things they were doing with the high performance ceramic filters were very good. Too bad Murata decided to discontinue everything but their 4 and 6 element ceramic filters. Pete wrote in message ups.com... do you know how to spell ? (besides being gross) |
Hi Steve,
When I owned my first AR7030 receiver in 1996-1998, I used a Kiwa preamp with it. If you'll take a look at my AR7030 review on www.radiointel.com (or elsewhere on the Web) you'll see that Craig at Kiwa measured a noise figure of 11.8 dB with the radio's internal preamp on, and 10.3 dB with the Kiwa preamp on (and internal preamp off). This 1.5 dB improvement is too little to be noticed by ear, but the higher specifications of the Kiwa device degraded the frontend performance (IP2, IP3, and dynamic range) less than the AOR's stock internal preamp. Here are the figures Craig measured on my AR7030 in his shop: 3rd Order Intercept measured at 12 MHz with the Preamp ON: +9.75 dBm 3rd Order Intercept measured at 12 MHz with the Kiwa SW Preamp: +19.5 dBm I said the following in my AR7030 review: "Word is spreading among AR7030 owners about the usefulness of a quality preamplifier, particularly when used on DXpeditions and in other low-noise surroundings. On a recent West Coast USA DXpedition in Washington State, most participants used Kiwa Electronics Broadband Preamplifiers and Shortwave Preamplifiers. Receivers included the NRD-535, Drake R8 and R8a, ICOM R-71a and the AR7030. The Kiwa devices provided audibly better S/N ratios on weak tropical band signals and foreign (split frequency) mediumwave DX targets. I believe more strongly now than when I first bought my AR7030 that the receiver can use a preamplifier like the Kiwa models with excellent overload immunity and noise characteristics. The AR7030's built-in preamp does not provide the same level of improvement." The key phrase here is "low-noise surroundings". At a Pacific NW coastal DXpedition location, particularly in mid-winter, the bands can be eerie-quiet. The band noise can drop the lowest during--and for an hour or two after--local sunrise. If this coincides with a few days of quiet solar activity, watch out! The opportunity to snag some excellent, weak DX is very good... DX that would normally be obscured by band noise. It is in these situations that a quality, low-noise preamplifier like the Kiwa model is useful (compared to a mediocre preamp like in the stock AR7030). The difference is not dramatic... in fact, it is slight, and may not even be noticed by the casual SWL or MW listener. However, it is another "edge" in performance for the dedicated DXer and a useful tool which surpasses the preamps in most receivers. Let me emphasize that the S/N ratio improvement with the Kiwa preamp was *slight* (but noticeable), and ONLY when I was on DXpeditions to the coast. At my home in the Seattle/Tacoma area, I could find no difference between the Kiwa and the stock AR7030 preamp regarding S/N ratio due to the much higher noise levels. However, I had fewer intermod products and garbage from local powerhouse mediumwave stations appearing in the 2000-3000 kHz range when using the higher grade Kiwa preamp. This week I asked Craig about the questions in this r.r.s. thread, and here was his response for the group: "The Noise Figure of the receiver is established in the front end or the RF amplifier. If an external preamp is included in the signal path that is quieter than the internal preamp than the Noise Figure improves. The internal preamp must be disabled for this to occur. I have measured the Noise Figure of numerous receivers and an improvement using the Kiwa preamp instead of the internal preamp is nearly always universal. If the internal preamp is exceptionally quiet there will be no change. I have never found a receiver where the Kiwa preamp degrades the Noise Figure. Will the owner hear the difference? If the improvement is only 1-2 dB, I doubt if it could be heard under typical/normal circumstances (urban environment with typical noise levels). However, if the dB improvement is significant and if a super low noise antenna is used the improvement should be noticeable when listening to difficult signal conditions." For a number of years now I've used a preamp module from Wellbrook Communications which Andy Ikin built into the K9AY antenna control box he used to market. This is an even higher performance preamp than Kiwa's, and it has an IP3 of +43 dB and a 1 dB compression point of +25 dBm. This is one very RF-sturdy preamplifier! The bottom line? Most people won't notice the difference between a quality preamp and an average one, but it does exist. However, for rummaging around for DX at the noise floor in an exceptionally low-noise environment, you want to use the best system components available. Guy Atkins Puyallup, WA USA mod. IC-756Pro & mod. R-75 Kiwa MAP / ERGO 450 & 700 ft. West & NW Beverage antennas wrote in message oups.com... According to Kiwa's website, their shortwave preamp will make your receiver quieter. They claim that when you turn off your receiver's internal preamp and instead rely upon the Kiwa preamp, you will have fewer noisy circuits operating inside the receiver. I find myself unmoved by this claim, since it would apply to *any* external preamp--and most external preamps will do nothing to improve S/N ratio, at least in my (limited) experience. Of course, the Kiwa preamp also has a BCB rejection filter. I *do* see how this could improve S/N ratio, but I'd like to hear some first hand reports. If you've used Kiwa's preamp, can you comment on whether it resulted in a significantly improved signal to noise ratio? Thanks in advance, Steve |
In article ,
"Pete KE9OA" wrote: I think you should buy the preamp if you think you will like it. I think that the reason nobody on this NG seems to have the Kiwa preamp is because they all have decent receivers. With a halfway decent receiver, you don't need a preamp. The trend in recent years has been to use NO RF amplification ahead of the 1st mixer. In the tube days, an RF amp was generally needed, because of the use of pentagrid convertors, etc. Exceptions were the R390 (at least the 1970s unit I had), which used a 6C4 1st mixer, the Squires Sanders IBS Superhet and their amateur version (SSR-1 or SS1-R?), which used a 7360 balanced mixer. If you have a good NF, there is no need for a preamp. A case in point...........even though the Kiwa preamp, which is very good, has an IP3 of +34dBm, the gain that the preamp provides still degrades the IP3 of the receiver itself by that same amount. +34dBm is ok for a high level preamp, but it is possible to design an RF preamp that has a +40dBm IP3. In all fairness to Kiwa, the preamp is very reasonably priced. I once looked at a schematic of the regenerative preamp for the Kiwa loop.............a very good design. The things they were doing with the high performance ceramic filters were very good. Too bad Murata decided to discontinue everything but their 4 and 6 element ceramic filters. The only reason I can see for a pre-amp would be a very low gain (small size) antenna such as a small loop. A table top radio with a full size antenna would probably not get much benefit from an amplifier. The only other exception to this was the very low noise surroundings example previously posted. -- Telamon Ventura, California |
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